Regeneration (Doctor Who)

In the long running British science fiction television series Doctor Who, regeneration is a biological ability exhibited by the Time Lords, a race of fictional humanoids originating on the planet Gallifrey. This process allows a Time Lord who is old, wounded or otherwise dying to undergo a transformation into a new physical form and a somewhat different personality. The process has been used eleven times throughout the history of the franchise as a device for introducing a new actor for the lead role of its main character, the Doctor. The current incarnation of the Doctor is played by Peter Capaldi, following the regeneration of the Eleventh Doctor (portrayed by Matt Smith) during the 2013 Christmas special "The Time of the Doctor". Other Time Lords and similar characters have also regenerated, for various reasons, sometimes with change of actors.

Conceptual history

Inspiration

The concept of regeneration was created in 1966 by the writers of Doctor Who as a method of replacing the leading actor. The role of the Doctor had been played by William Hartnell from the programme's inception in 1963 but, by 1966, it was increasingly apparent that Hartnell's health was deteriorating and he was becoming more difficult to work with. Producer John Wiles had, following several clashes with Hartnell, intended to have the actor replaced in The Celestial Toymaker; during two episodes of that serial, the Doctor is invisible (owing to Hartnell being on holiday during the recording). Wiles' plan was for the character to reappear played by a new actor. This proposal was vetoed by Gerald Savory, the BBC's Head of Serials (and Wiles' superior), which led to Wiles leaving before The Celestial Toymaker was produced.^[1] However, it was apparent that it would not be possible for Hartnell to continue for much longer.

On 29 July 1966, production concluded on the final episode of The Smugglers, the last serial recorded in the third production block.^[2] During production, Hartnell and producer Innes Lloyd had reached an agreement that he should leave the role, having starred in one more serial that would see a handover to a new actor, which would be the first one produced as part of Season 4. Script editor Gerry Davis proposed that, since the Doctor had already been established as an alien, the character could die and return in a new body. Lloyd took this further by suggesting that the Doctor could do this "renewal" regularly, transforming from an older man to a younger one; this would allow for the convenient recasting of the role when necessary.^[3] The process itself was modelled on LSD trips, with the experience being like the "hell and dank horror" of taking the drug.^[4]

At the conclusion of The Tenth Planet, the First Doctor collapses from apparent old age and exhaustion, having commented earlier that his body was "wearing a bit thin". Then, before the eyes of his companions Ben and Polly, and of the viewing audience, his features shift into that of the Second Doctor, played by Patrick Troughton. In The Power of the Daleks, the Second Doctor's first story, the Doctor draws an analogy between the renewal and a caterpillar turning into a butterfly.^[5]

Developing the concept

It was not clear initially whether the renewal was a natural ability of the Doctor's as opposed to a process initiated by technology. In Power of the Daleks, the Second Doctor describes his renewal as a function of his TARDIS time machine, stating that "without it, [he] couldn't survive."^[5]

When Troughton left the series in 1969, the Doctor was renewed again, but this time the change was forced on him by the Time Lords at the conclusion of The War Games, where it is referred to as a "change of appearance". As with the first change, this language suggested only a superficial physical change, not one of personality, although Jon Pertwee's portrayal of the Third Doctor also differed quite substantially from Troughton's. Unlike the previous change, this one is treated as a punishment rather than a natural process: in The War Games the Doctor protests, "You can't just change what I look like without consulting me!"

As the series continued, more aspects of the regenerative process were introduced, but the basic concepts of regeneration as accepted by fans of the series today were only firmly established in the final scene of Planet of the Spiders (1974), when Pertwee's Third Doctor turns into Tom Baker's Fourth Doctor. In this scene, the change is called "regeneration" for the first time, and is explained as a biological process that occurs when a Time Lord's body is dying. It is also stated that following the regeneration the Doctor's brain cells would be shaken up and his behaviour would be "erratic" for a time, something that would be true for most subsequent regenerations.

In the About Time reference series Lawrence Miles and Tat Wood note that the officially licensed magazine, Doctor Who Monthly, stated in a "Matrix Data-Bank" column in 1982 that its readers should not confuse the "regenerations" of later incarnations with the "rejuvenation" of Hartnell into Troughton.^[6] However, dialogue within the series itself explicitly includes the First-to-Second "rejuvenation" when enumerating the Doctor's regenerations (for example in Mawdryn Undead (1983), The Five Doctors (1983), the 1996 television movie, "The Next Doctor", "The Eleventh Hour", "The Lodger", "Nightmare in Silver" and "The Name of the Doctor").

Transitions

The regeneration "effect" was accomplished during the series' original run from 1963–1989 primarily through the use of video mixing. Originally, the plan was to have Hartnell collapse at the end of The Tenth Planet with his cloak over his face, which would then be pulled back to reveal Troughton in the next serial. However, vision mixer Shirley Coward discovered and took advantage of a malfunction in the mixing desk which allowed Hartnell's image to be overexposed to the point of almost whiting out the screen, then fading back in to reveal Troughton's face. This also meant that the regeneration scene could take place with both actors at the conclusion of The Tenth Planet, and Troughton was accordingly signed up to participate.^[3]

Subsequent regenerations retained essentially the same method, with or without additional video or make-up effects. The transition from the Fourth to the Fifth Doctor used an additional make-up effect representing a transitional form known as the Watcher, but aside from this, other regenerations in the original series run simply mixed the image of the incoming actor on top of the outgoing one. The transition from the Seventh to the Eighth Doctor in the 1996 television movie took advantage of the higher budget and modern computer animation technology to "morph" the features of Sylvester McCoy into those of Paul McGann.

With the exception of the transitions from the Second to Third, each regeneration was shown on-screen, with the previous incumbent in the role symbolically "handing off" the character to the next. The Second Doctor was never seen to actually change into the Third, simply fading off into darkness at the end of The War Games and then stumbling out of the TARDIS, already regenerated, at the start of Spearhead from Space (1970).

The regeneration of the Sixth Doctor into the Seventh is the only time that a single actor took on the roles of two incarnations of the Doctor. Colin Baker declined the invitation to film the regeneration sequence at the start of Time and the Rani (1987) due to the circumstances in which the BBC dismissed him from the role.^[7] As a result, Sylvester McCoy had to don his predecessor's costume and a blond curly wig, lying face down, with the mixing effect to the Doctor's "new" features occurring as he was turned over.

The 2005 series, which revived the programme after its cancellation 16 years earlier, began with the Ninth Doctor already regenerated and no explanation given as to the circumstances behind the change (although a scene in the debut episode "Rose" when the Doctor commented on his appearance in a mirror indicated that the change had recently occurred). In the documentary series Doctor Who Confidential, producer Russell T Davies explained his reasoning that, after such a long hiatus, a regeneration in the first episode would be not only confusing for new viewers but also lacking in dramatic impact, as there would have been no emotional investment in the character being replaced.^[8] The regeneration into the Ninth Doctor was later seen and explained in "The Day of the Doctor" (2013).

The regeneration of the Ninth Doctor into the Tenth at the end of "The Parting of the Ways" (2005) used computer effects to morph Christopher Eccleston into David Tennant. In the episode of Doctor Who Confidential accompanying the episode "Utopia" (2007), where the effect is used for the Master's regeneration, it is stated that the production team decided that this would be a common effect for all future Time Lord regenerations, rather than each regeneration sequence being designed at the whim of the individual director. This style of transition is seen again in "The Stolen Earth"/"Journey's End" (2008) both when the Doctor undergoes an abortive regeneration, and when his hand spawns a clone in the second part; in The End of Time (2010) during which Matt Smith took over the role as the Eleventh Doctor; in "The Impossible Astronaut" when the Doctor is shot twice and seemingly killed; in "Day of the Moon" when a young girl regenerates; and in "Let's Kill Hitler" when Mels (Nina Toussaint-White) is shot and regenerates into River Song (Alex Kingston). "The Night of the Doctor" and "The Day of the Doctor" subsequently use the effect to show the Eighth Doctor and War Doctor's regenerations respectively. The Eighth Doctor's regeneration into the War Doctor uses steady beams of light as opposed to the flame effect used for other revived series regenerations.

The regeneration from the Eleventh Doctor to the Twelfth slightly differs from the other regenerations from the revived series. During "The Time of the Doctor", the Eleventh Doctor reveals that he has used all his regenerations and is in fact in his thirteenth and final body, leading to his aged appearance during the events of the episode. At the conclusion, the Time Lords grant him a new regeneration cycle, and he begins his thirteenth regeneration in the explosive manner that has become tradition (so explosive that it destroys an invading Dalek including a ship in the process). However, as this regeneration is the first in a new cycle, it initially only "resets" his current body back to its youthful appearance (the Doctor referring to this as the cycle "breaking in"), and the eventual transition to the Twelfth Doctor happens with a flash and the actor suddenly lurching back, standing back up to reveal the new Doctor.

Characteristics within the series

Relationship with the TARDIS

The TARDIS appears to assist in the regenerative process, as suggested by the Second Doctor's statement to this effect shortly after regenerating from the First. This is reiterated by Jack Harkness' insistence that the Doctor be taken into the TARDIS having been shot by a Dalek in "The Stolen Earth". Of the six occasions on which the Doctor has regenerated outside the TARDIS: one is forced on him by the Time Lords (Second to Third Doctor, The War Games); one requires a Time Lord to give the Doctor's cells a "little push" to start the process (Third to Fourth, Planet of the Spiders); one results in his being dependent on the TARDIS's "Zero Room", a chamber sealed from all outside forces, to help him recover (Fourth to Fifth, Castrovalva); one occurs a few hours after he has actually "died" (Seventh to Eighth, the 1996 television film; the delay at is, however, shown to have been caused by anæsthetic, rather than the Doctor's distance from the TARDIS); one is induced by the Sisterhood of Karn after reviving the Doctor from actual death (Eighth Doctor, "The Night of the Doctor"). The Seventh to Eighth regeneration remains the only one that takes place significantly far away from the TARDIS, without any obvious interaction from other Time Lords and results in the Doctor suffering near-complete amnesia for nearly a day until an event inside the TARDIS triggers his memories to return. The future Eleventh Doctor is killed in mid-regeneration, showing he is vulnerable to death while regenerating and as such his need for the TARDIS may be for safety rather than aid. However it is later revealed that this regeneration was indeed a simulation since the Doctor who was shot was actually a Teselecta robot. The Eleventh Doctor starts his regeneration outside the TARDIS though he does end it inside it.

Energy release and increased strength

The exact mechanism that makes regeneration possible is not stated in the television series, but it is generally assumed in the spin-off media that the ability to regenerate may be linked to what is known as the "Rassilon Imprimatur", the symbiotic nuclei of a Time Lord that bonds him or her to a TARDIS, and allows his or her body to withstand the molecular stresses of time travel (The Two Doctors, 1985).^{[note 1]}

In "The Christmas Invasion" (2005) it is stated that the regenerative cycle generates a large amount of energy that suffuses the Time Lord's body, and also shown that residual effects from a regeneration allow him to grow back a hand within the first 15 hours after the initial start of the regeneration. Accordingly, in "Let's Kill Hitler", River Song is able to repel bullets after regenerating. She is later able to send off an energy wave soon after her regeneration, though this particular feat may be one of the abilities gained during the first 15 hours after a regeneration.

In the series four finale of the revived series, "Journey's End", an injured Tenth Doctor manages to avert a full regeneration by channelling "excess regenerative energy" into his severed hand, allowing him to heal without changing form. The limb ends up developing into a half-human clone when Donna Noble touches it; the event, a "two-way" "Human-Time Lord Meta-Crisis", also gives Donna a Time Lord's mind.

Increased strength is sometimes a temporary by-product of regeneration. In the moments following his regeneration into his eighth incarnation, the Doctor possessed enough physical strength to batter a steel door completely off its hinges. Also the Fourth Doctor karate chopped a brick in half shortly after his third regeneraton, and was unable to repeat the action later in the same serial.

In The End of Time when the Tenth Doctor regenerates into the Eleventh Doctor, the release of energy damages the TARDIS to the extent that components fall, the door's windows smash and the TARDIS then flies uncontrollably over Earth before crash-landing in Amy Pond's garden. Later, when the Eleventh Doctor begins his regeneration into the Twelfth Doctor in "The Time of the Doctor", he is able to control his regeneration energy and send out energy blasts that obliterated nearby Daleks and an entire Dalek saucer. The release of energy caused a shockwave that severely damaged the town in which the regeneration took place.

Personality change

With regeneration also comes a change of personality. The viewing audience sees this most often and most dramatically in the differing quirks and personality traits of the Doctor's various incarnations. The Doctor's core personality traits of heroism and intolerance of injustice are still retained, but in The End of Time the Tenth Doctor laments that demise of his current incarnation, with its own personality and attributes, makes for something much akin to an actual death. His last words before regenerating are "I don't want to go."

Shortly after the regeneration process, the Doctor sometimes goes through a period of physical and psychological instability. The Second Doctor experiences crippling pain after his first regeneration (in The Power of the Daleks), the Third Doctor collapses out the TARDIS following his regeneration (in Spearhead From Space), the Fourth Doctor started rambling random phrases and possessed a higher than usual strength that he could cut a brick in half merely with his hand (in Robot), the Fifth Doctor (in Castrovalva) begins reverting to his previous personalities and the Sixth Doctor experiences extreme paranoia, flying into a murderous rage and nearly killing his companion (The Twin Dilemma, 1984). The Eighth Doctor experienced amnesia as a result of post-regeneration trauma (the 1996 television film); uniquely, the Doctor was "not alive" at the time of this regeneration. The regeneration from the Ninth to the Tenth Doctor sees the Doctor experiencing sudden spasms and great pain ("Children in Need special"), and later being unconscious for most of the next fifteen hours ("The Christmas Invasion"). The regeneration from the Tenth to the Eleventh doctor caused the Doctor to experience strange food cravings, only to be disgusted by them upon actually trying them ("The Eleventh Hour"). The Twelfth Doctor forgot how to fly the TARDIS (as well as the name of the TARDIS) right after the regeneration process in The Time of the Doctor. The Brain of Morbius implies that Time Lords other than the Doctor may experience difficult regenerations, since the Sisterhood of Karn had been supplying them with an "elixir of life" that could assist the process. In "The Night of the Doctor", the Sisterhood tell the Eighth Doctor they can provide elixirs to give rise to non-random regenerations, allowing the Doctor to specify either a physical type or personality.

The Master showed a dramatic personality change upon regenerating into the Mistress/Missy. In that form, she wants nothing more than to renew her bond with the Doctor, even calling him her "boyfriend" at one point. ("Deep Breath, Death in Heaven") When she met him again, Missy pretended to be an android and kissed him passionately. ("Dark Water")

Extent of physical change

The Doctor has always regenerated into the form of a humanoid male. However, when explaining the process of regeneration to Rose at the end of "The Parting of the Ways", the Ninth Doctor suggests that his new form could have "two heads", or even "no head", and in the 2005 Children in Need special, which takes place immediately after that episode, the newly regenerated Tenth Doctor, while examining his new body, makes a point of checking that he has two arms, two legs and two hands, implying that regenerations can sometimes result in physically deformed or non-humanoid forms; it is not clear whether or not these two moments are intended as jokes.

In the second part of The End of Time (2010), the Eleventh Doctor also enumerates eyes, ears, hands, fingers, and legs, and after feeling his hair, even wonders for a moment if he has changed sex. In a later episode, "The Doctor's Wife," the Doctor refers to another Time Lord, the Corsair, having been both male and female in various incarnations. Among the regeneration options offered by the Sisterhood of Karn to the Eighth Doctor in "The Night of the Doctor" is to choose becoming either a man or a woman. "Dark Water/Death in Heaven" proves a Time Lord can change gender through regeneration when the Master is depicted in a female incarnation ("Missy"). In "Hell Bent," the elderly white male General regenerates into a younger, black woman.

In spin-off media, however, more drastic changes have been depicted. For example, in the Big Finish Productions audio Circular Time, a Time Lord known as Cardinal Zero regenerates into an avian life-form after being poisoned.^[9]

Control over regeneration

The Doctor's regenerations are always involuntary, and he has no control over his final appearance. In "The Parting of the Ways", the Ninth Doctor describes the process as "a bit dodgy"—i.e., somewhat dangerous or uncertain—and the Tenth Doctor refers to regeneration as "a lottery" ("The Day of the Doctor"). For example, despite an apparent wish for this to occur, neither the Tenth nor the Eleventh Doctors regenerated into redheads. The sole known exception to this is the Eighth Doctor's regeneration into the War Doctor ("The Night of the Doctor"), as the Doctor was able to consume a potion made by the Sisterhood of Karn which ensured his next body was a warrior able to fight in the last Great Time War, though he didn't appear to make any specifications about the actual physical appearance. The Doctor was also once given the chance to choose his appearance upon his forced regeneration by the Time Lords in "The War Games" but rejected all of the options presented to him. The Time Lords grew tired of his stalling and thus sent him away to regenerate into the Third Doctor, an apparently random result. Alternatively, the Tenth Doctor was shown twice to exert control over regenerating, attributed by the Eleventh Doctor to "having vanity issues at the time." In "Journey's End", after being shot by a Dalek triggered a regeneration, the Tenth Doctor used the regeneration energy to heal his wounds, then channeled the remaining energy into his severed hand and purposely kept his current appearance. When he finally did regenerate into the Eleventh Doctor, he still consciously prevented himself from regenerating to prolong his time as his current incarnation for several hours. Doing this caused a more explosive regeneration that nearly destroyed the TARDIS.

In contrast, the first episode of "Destiny of the Daleks" depicts Romana undergoing a voluntary regeneration, in which she tries out several different forms before choosing to adopt the appearance of Princess Astra, a person she encountered in a previous adventure ("The Armageddon Factor"). Many writers of spin-off media have attempted to rationalise the difference between the Doctor's and Romana's regenerations. Doctor Who television writer and script editor Eric Saward suggests in his 1985 novelisation of The Twin Dilemma (1984) that Time Lords can control the appearance of their next body if they trigger the regeneration voluntarily, but not if the regeneration is caused by death or injury. The Doctor Who Role Playing Game by FASA suggests that some Time Lords have a special ability to control their regenerations. The fan reference book The Discontinuity Guide suggests that Romana's various "try-ons" were projections of potential future incarnations like the K'anpo Rinpoche/Cho Je situation in Planet of the Spiders.^[10] Miles and Wood's About Time also mentions this while theorising that the Time Lords had improved the technology of regeneration since the Doctor's time; Romana, being of a later generation than the Doctor, would therefore have finer control over the regenerative process in its early stages.^[11]

Other moments in the series suggest that other Time Lords have more control over their regeneration than that usually displayed by the Doctor. Prior to regenerating in the episode "Utopia", the Master expresses a desire to be "young and strong" like the Doctor and transforms accordingly. Subsequently, in "Last of the Time Lords", he is able to prevent regeneration at will, refusing to regenerate after being shot by Lucy Saxon, despite the Doctor's pleas. In "The Stolen Earth," the Doctor begins to regenerate in a cliffhanger moment, but at the start of "Journey's End" (the episode that followed), he interrupts the process after healing his bodily injuries, redirecting the remaining regeneration energy into his preserved hand. In "Let's Kill Hitler", when Mels begins to regenerate into River Song, she says she is trying to concentrate so she can come out a particular dress size. In "Nightmare in Silver", the Eleventh Doctor suggests that he can trigger regeneration voluntarily, using the suggestion to threaten the Cyber-Planner invading his body and mind, saying "I could regenerate now. Big blast of regeneration energy, burn out any little Cyber widgets in my brain, along with everything you're connected to. Don't want to. Use this me up, who knows what we'll get next? But I can." In "The Girl Who Died, The Twelfth Doctor speculates that he deliberately, if not subconsciously, chose the form of Caecilius (from "The Fires of Pompeii") to remind himself that he is a man who always saves people, even if it is just one.

Recognisability of the regenerated

The television series is inconsistent on the question of whether Time Lords can recognise each other across regenerations. For example, in The Deadly Assassin an old classmate of the Doctor's, Runcible, is slow to recognise the Doctor in his fourth incarnation, and once he has, it then takes him a while to realise that his appearance has changed. However, in The Armageddon Factor (1978), Drax, another old classmate, recognises the Fourth Doctor immediately although they had not seen each other since the Academy (the Doctor takes a while to remember Drax, though).

There is also inconsistency as to whether the Doctor can recognize his own future incarnations. In the original series, the Doctors usually have no difficulty recognizing one another (in The Three Doctors, the First, Second, and Third Doctors all know one another on sight. However, in The Five Doctors, the First Doctor does not recognize the Fifth Doctor as himself and needs to be introduced by the Fifth as his fourth incarnation.

The Daleks' ability to recognise the Doctor also varies: they recognise him outright in The Power of the Daleks but need confirmation from others in Revelation of the Daleks and "Doomsday". In Asylum of the Daleks, the Daleks' knowledge of the Doctor is tied to a psychic link among them called the path-web, which he hacks to make them forget him. The Cybermen have their own method of recognising the Doctor, usually through his past incarnations, as seen in Earthshock and "The Next Doctor".

Maximum number of regenerations in a cycle

In The Deadly Assassin (1976) the Fourth Doctor states that Time Lords can regenerate twelve times in a cycle (enabling thirteen incarnations). This was confirmed in the introduction of the 1996 television movie, and in "The Time of the Doctor" (2013). The matter of whether the Doctor was limited to thirteen incarnations became increasingly significant as the number of actors to play the role grew. The BBC's Series 4 FAQ^[12] suggested that now that the Time Lord social order had been destroyed, the Doctor may be able to regenerate indefinitely: "Now that his people are gone, who knows? Time Lords used to have 13 lives." In Death of the Doctor (a 2010 The Sarah Jane Adventures serial), the Eleventh Doctor says he can regenerate 507 times (early news reports, before the episode was broadcast, suggested he would say there is no limit to the number of regenerations).^[13] However, writer Russell T Davies explained in an interview with SFX that this line was not intended to be taken seriously and insisted that the "thirteen lives" rule was too deeply entrenched in the viewer consciousness for his throwaway line to affect it.^[14]

Episodes in the classic series later confirmed the twelve regenerations limit. For example, the Fifth Doctor explicitly states in Mawdryn Undead that he has regenerated four times and has only eight regenerations left. In the TV movie, the Doctor (played by Paul McGann) says that he was "nearing the end of [his] seventh life" when referring to the Sylvester McCoy incarnation in flashback. The Doctor also states that "a Time Lord has thirteen lives".

However, the series has depicted exceptions to this rule in the career of the renegade Time Lord the Master. When the Master finds himself at the end of his regenerative cycle in The Keeper of Traken (1981), he takes possession of the body of another person to continue living although he was using the Source of Traken to bind his mind to the body. In The Five Doctors (1983), the Master is offered a new cycle of regenerations by the High Council of the Time Lords in exchange for his help. In the 1996 television movie, the Master is able to (temporarily, he says) inhabit the body of a human, and attempts to take the Doctor's remaining regenerations (though since the attempt is thwarted, it is not clear if it would have worked). In "The Sound of Drums" (2007), the Master is revealed to have been granted a new body by the Time Lords during the Time War.

The number of previous incarnations of the Doctor was at first unclear within the series. In the Fourth Doctor story The Brain of Morbius, the Doctor participates in a mental ‘duel’ with another Time Lord and the machine to which their minds are connected begins to project the faces of the "losing" contestant’s regenerations in chronologically descending order. As the Doctor is overpowered by Morbius, the images change successively to those of the third, second and first Doctors, then eight further faces appear. It was the intention of producer Philip Hinchcliffe and script editor Robert Holmes that images were even earlier incarnations of the Doctor.^[15][16] However, the narrative does not explicitly confirm that the faces do represent incarnations of the Doctor, even though, as the faces are shown, Morbius cries "How far Doctor? How long have you lived?", indicating that they are not incarnations of Morbius, but rather that it is the Doctor's past being shown.^[17]

In other episodes, it was firmly established that the William Hartnell incarnation of the Doctor was the very first. In The Three Doctors, the Time Lord President describes the Hartnell incarnation as "the earliest Doctor". This is cemented in The Five Doctors when Peter Davison's Fifth Doctor (introducing himself to the First Doctor) says that he is the fourth regeneration, meaning that there have been five of him. The First Doctor also refers to himself as "the original". Episodes of the revival series showing the lives of the Doctor -- "The Next Doctor", "The Eleventh Hour", "The Day of the Doctor" and "The Husbands of River Song"—all begin with the William Hartnell incarnation.

In "The Lodger", after the Eleventh Doctor shows Craig who he is, he points to his face and says, "Eleventh". However, in "The Name of the Doctor", when the Doctor rescues Clara from inside his own time stream, they both see another figure that Clara doesn't recognise. The Doctor then reveals that this is a past incarnation that he deemed unworthy of the name "Doctor" due to the atrocities he committed during the Time War, and only accepted him after learning the truth of how the war ended ("The Day of the Doctor").^[18] Ultimately, in "The Time of the Doctor" the Eleventh Doctor reveals that, counting the War Doctor and the Tenth's aborted regeneration, he is actually in his final incarnation. However, at the behest of Clara, the Time Lords grant the Doctor a new regeneration cycle, allowing a thirteenth regeneration into an incarnation known as the Twelfth Doctor.

In "The Time of the Doctor", the Eleventh Doctor describes his new regeneration ability as a 'cycle', implying that he's been restored to the customary twelve regenerations. However, in "Kill the Moon", the Twelfth Doctor says he's "not entirely sure [he] won't keep regenerating forever," once again raising the question regarding any limits to this ability. In "Hell Bent", the President asks the Doctor "How many regenerations did we give you?", further implying that the Doctor has a finite number of regenerations, but the exact amount remains undetermined.

Temporary potential future incarnations

In some cases, future potential incarnations can achieve independent, though temporary, existence. In Planet of the Spiders, a Time Lord, K'anpo Rinpoche, creates a corporeal projection of a future incarnation which has such an existence under the name Cho Je until he regenerates into that incarnation. The Valeyard, an "amalgamation of the darker sides of [the Doctor's] nature, somewhere between [his] twelfth and final incarnation", appears in The Trial of a Time Lord (1986) opposite the Sixth Doctor; the Valeyard is promised the remainder of the Doctor's regenerations. Another example is "The Watcher", who repeatedly appears to the Fourth Doctor in Logopolis (1981), and ultimately merges with him as part of his regeneration into his fifth incarnation.

The Time Lords' ability to change species during regeneration is referred to in the television movie by the Eighth Doctor in relation to the Master. Mavic Chen states that the First Doctor's resemblance to an Earth creature is "only a disguise" in The Daleks' Master Plan (1965). In Destiny of the Daleks (1979), the Fourth Doctor's Time Lady companion Romana demonstrates an apparent ability to "try on" different bodies from a number of different species during her regeneration, before settling on a final, humanoid form which physically resembles Princess Astra of Atrios (see discussion below).

Steven Moffat has said that reference will be made to Peter Capaldi's previous appearances in the Whoniverse during his tenure as the Twelfth Doctor: "The face is not set from birth. It’s not like he was always going to be one day Peter Capaldi. We know that’s the case because in The War Games he has a choice of faces. So we know it’s not set, so where does he get those faces from? They can’t just be randomly generated because they've got lines. They've aged. When he turns into Peter he’ll actually have lines on his face. So where did that face come from?” In "Deep Breath" (2014), the Doctor and several other characters speculate about where his new face came from, given that it has lines from frowning. The Doctor considers aloud that it is a face he recognises from somewhere, but due to post-regenerative trauma, he cannot place it. In "The Girl Who Died" (2015), he concludes that he subconsciously chose the face as a reminder of his decision to save the life of Caecilius (also played by Capaldi) in "The Fires of Pompeii" (2008).

Regeneration of non-Gallifreyans

The fact that the Master is inhabiting a non-Gallifreyan body when he is offered a new cycle of regenerations (see above) implies that it is possible to grant them to a non-Gallifreyan, albeit one inhabited by a Time Lord mind. In addition, River Song is shown to have the ability to regenerate due to altered DNA that has similarities to Time Lord DNA, a side effect of having been conceived on board the TARDIS as it travelled through the space-time vortex. Non-Gallifreyans are also seen to regenerate in Underworld (1978) and Mawdryn Undead (1983), but with adverse side effects. In Mawdryn Undead, these appear to be the result of mishandling stolen technology, but in Underworld they are implied to be the inevitable result of limited technology that reinvigorates, rather than transforms, the subject's appearance (in this case, the Minyans, with whom the Time Lords shared much of their technology), thereby regenerating 'the body, not the soul'.

Failed regeneration

It has been suggested in the series many times that regeneration is not guaranteed and can fail. After his cellular structure is decimated by the Metabelis crystals in Planet of the Spiders, the Third Doctor's regeneration requires "a little push" from fellow Time Lord K'anpo Rimpoche before it can proceed. As he succumbs to spectrox toxaemia in The Caves of Androzani, the Fifth Doctor says, "I might regenerate... I don't know... It feels different this time...". He then hallucinates, seeing his former companions encouraging him to survive, before the Master overwhelms them all, telling him he must die. The 1996 TV movie showed the Doctor's regeneration delayed for more than three hours, with the Eighth Doctor later remarking that the fact his Seventh incarnation was under anaesthesia at the time of his "death" could have "destroyed the regenerative process", and that he was "dead too long this time" prior to his regeneration. In many episodes, the Doctor doubts his own survival, though it is not always clear whether such statements refer to the death of only that particular incarnation. (The only time he makes a completely unambiguous distinction between these two scenarios – in The End of Time – he makes it clear that he regards regeneration as nearly as bad as death, because as he sees it, he dies and "a new man" walks away). In The Mind of Evil the Master points a conventional firearm at the Doctor and threatens to "put a bullet through both [his] hearts," while in "Forest of the Dead", Professor Song warns that electrocution would stop both the Time Lord's hearts, killing him. In "Turn Left", in which the Tenth Doctor dies in a parallel world, a UNIT member speculates that what happened to the Doctor "must have happened too fast for him to regenerate." In the first part of The End of Time, the Doctor tells Wilfred Mott that if he is killed before the regeneration can start, then it will fail.

In the series 6 premiere, "The Impossible Astronaut", a future version of the Eleventh Doctor is shot twice by the titular astronaut and begins to regenerate. However he is then shot again and dies, showing that not only can he be killed before regeneration, but also while the change is taking place. (However, the later revelation, in "The Wedding of River Song" that what was shot was in fact a mechanical avatar of the Doctor and not the real person calls this into question.) In the episode "Let's Kill Hitler", the Doctor is poisoned by River Song using a poison which also disables the ability to regenerate and seemingly dies, although he is later revived when River gives up her remaining regenerations to save him. "The Time of the Doctor" later shows that the Doctor did not have any remaining regenerations at this time anyway.

In the mini-episode "The Night of the Doctor", the Eighth Doctor is killed when the ship he is on crashes onto the planet Karn, reinforcing the idea that a sudden, traumatic death may prevent regeneration. The Sisterhood of Karn explain that he was, in fact, dead, but they were able to use their Time Lord-based technology to revive him and force a regeneration anyway.

In "Heaven Sent", the Twelfth Doctor is badly burned by the Veil, preventing him from regenerating. However, as his prison reset itself after he left a room, he used what was left of his life to bring a past version of himself out of the teleporter. This cycle continued for 4.5 billion years, according to the episode "Hell Bent" as he chips away at a wall blocking a portal back to Gallifrey.

Transference of regenerative energy

In Mawdryn Undead (1983), it is first stated that a Time Lord can transfer his regenerative life essence to another being. In that story, the Fifth Doctor is coerced by Mawdryn to give up his future regenerations in order to cure Nyssa and Tegan Jovanka from Mawdryn's disease. Although the transfer does not occur (due to the timely interference of Brigadier Lethbridge-Stewart), the Doctor states that the consequence of the transference would be that he would sacrifice his eight remaining lives and cease to be a Time Lord. It is not until "Let's Kill Hitler" (2011) that a similar transference is shown; in that instance, River Song sacrifices her own regenerative power in order to revive the dead Eleventh Doctor. The favour is returned in "The Angels Take Manhattan" in which River's wrist is repaired by the Doctor, who subsequently gives up a portion of his regenerative energy.

A major plot point of the 1996 TV movie involves the Master scheming to steal the Doctor's remaining regenerations for himself.

The Tenth Doctor also consciously aborts a regeneration in "Journey's End" and instead transfers the energy to his previously severed hand (from "The Christmas Invasion"), which had been saved in a container by Captain Jack Harkness; when Donna Noble touches it, it creates an entirely new person - a "meta-crisis" half-human Doctor. The Eleventh Doctor confirms, before himself regenerating during the events of "The Time of the Doctor", that this action used up a full regeneration, though he "kept the same face" - as stated in "The Time of the Doctor", he had vanity issues at the time.

In "The Witch's Familiar", the Twelfth Doctor offers a small amount of regenerative energy to Dalek creator Davros to sustain him in his dying minutes a bit longer. The Doctor says that doing so "may cost [him] an arm or a leg down the road". Davros, however, siphons off much more regeneration energy from the Doctor to revitalize himself and transform the Daleks on Skaro into superior hybrid creatures. His plan backfires when decaying Daleks—incapable of dying, and kept in an underground 'sewer' system when their effective 'lives' have expired—are also reenergized and attack the Daleks on the surface. The Doctor reveals that he expected such a plot and knew it would backfire.

Regenerations depicted in the series

The Doctor's regenerations

1. First Doctor (William Hartnell): "Renewed" by the TARDIS after collapsing from old age/exhaustion in The Tenth Planet.
2. Second Doctor (Patrick Troughton): A "change in appearance" imposed by the Time Lords in The War Games as a penalty for repeated breaching of their law of non-intervention.
3. Third Doctor (Jon Pertwee): Radiation poisoning on the planet Metebelis 3 in Planet of the Spiders.
4. Fourth Doctor (Tom Baker): Falls from the Pharos Project radio telescope in Logopolis.
5. Fifth Doctor (Peter Davison): Succumbs to spectrox toxaemia poisoning in The Caves of Androzani.
6. Sixth Doctor (Colin Baker): Regenerates after the TARDIS is attacked by the Rani and crash lands in Time and the Rani and due to exposure to focused beams of a radiation lethal to Time Lords consequent to the Rani's attack on the TARDIS.
7. Seventh Doctor (Sylvester McCoy): Shot by a San Francisco street gang in the 1996 TV film, he dies during surgery by doctors unfamiliar with his alien physiology, regenerating later in a morgue fridge (anaesthetic having slowed the process).
8. Eighth Doctor (Paul McGann): Killed in a spaceship crash on the planet Karn in the mini-episode "The Night of the Doctor". Temporarily revived by the Sisterhood of Karn, he drinks a potion they have prepared, initiating regeneration to a form suitable to fight in the Time War.
9. War Doctor (John Hurt): Regenerates from old age/exhaustion after the conclusion of the Time War in "The Day of the Doctor".
10. Ninth Doctor (Christopher Eccleston): Fatal cellular degeneration caused by absorbing the Time Vortex from Rose Tyler in "The Parting of the Ways".
11. Tenth Doctor (David Tennant): Shot by a Dalek in "The Stolen Earth". Reluctant to change his appearance, he heals himself using some regeneration energy, directing the remainder into his severed hand in "Journey's End".
12. Tenth Doctor (David Tennant): Absorbs a massive dose of radiation in place of Wilfred Mott in The End of Time.
13. Eleventh Doctor (Matt Smith): At the point of death from old age, he receives a new regeneration cycle from the Time Lords, allowing him to destroy the Daleks on Trenzalore and regenerate in "The Time of the Doctor".

Romana's regenerations

Romana's tongue-in-cheek regeneration scene in Destiny of the Daleks contrasts markedly with the Doctor's transformations. In the first episode of the serial, Romana undergoes regeneration, in the process trying out several different forms before choosing to adopt the appearance of Princess Astra, a character she encountered in a previous adventure (The Armageddon Factor).

Multiple attempts have been made in the spin-off media to explain the necessity for Romana's regeneration.

• In the short story "The Lying Old Witch in the Wardrobe" by Mark Michalowski, published in the Big Finish Productions anthology, Short Trips: Companions, unknown to the Doctor, Romana suffers damage due to exposure to the Key to Time. Just as she is about to regenerate, a humanoid manifestation of the TARDIS, jealous of Romana, traps her in a force field. It proceeds to pretend to be Romana, changing into different forms until finally becoming a double of Princess Astra. This manifestation is the one who appears in Destiny of the Daleks. Realising the error of its ways after that adventure, it releases Romana, but not before making the female Time Lord assume the image of Astra.
• The second explanation is given in the Gallifrey audio series. Gallifrey: Lies by Gary Russell reveals that Romana forced her own regeneration to prevent an ancient Gallifreyan evil called Pandora from gaining power over her (see also History of the Time Lords – Audio plays).
• The third explanation is in the Fifth Doctor audio story The Chaos Pool by Peter Anghelides, which states that the creators of the Key to Time re-disguised its final segment as Romana, which is why she changed and why she chose Astra's form.

The Master's regenerations

The Master has only been shown to regenerate once onscreen. To date, most of his new incarnations depicted onscreen are of either unspecified origins or are born of non-regeneration methods. (It is also never revealed onscreen which 'version' of the Master is the one first seen on the show, played by Roger Delgado.)

In The Deadly Assassin (1976) it is stated that the Master has used up all his regenerations, hence his decrepit appearance in that serial. He is attempting to use the artifacts of Rassilon to obtain a new cycle, but the process would destroy Gallifrey, so the Doctor intervenes. The Master subsequently takes over non-Gallifreyan bodies in order to extend his life. The first victim is Nyssa's father, Tremas, played by Antony Ainley in The Keeper of Traken (1981).

In The Five Doctors (1983) the High Council of Gallifrey offers the Master, (who is still using the stolen body of Tremas), a new regeneration cycle in exchange for his help with rescuing the Doctor. The Master agrees to the deal. Whilst searching for the Third Doctor in the inhospitable environment of the Gallifrey's Death Zone, The Master sees the charred and skeletal remains of one of his previous incarnations. He drily observes that this is "one of [his] predecessors". A thunderbolt later hits the skeleton. At the end of the episode, the Master is returned to his own time stream by Rassillon who announces that The Master's "sins will find their punishment in due time".

The Master continues to use the stolen body of Tremas for subsequent stories - Planet of Fire, and The Mark of the Rani; and The Ultimate Foe.

In Survival, it is discovered that the body of the Master has somehow become bewitched/infected from his visiting the home planet of the Cheetah People.

The Time Lords execute the Master at the start of the 1996 TV movie. He later possesses a non-Gallifreyan body, this time a human named Bruce.

In "Utopia" (2007) the Master regenerates naturally in his only on-screen regeneration to date. After being fatally shot by the insectoid creature Chantho, the Master regenerates from the incarnation known as Professor Yana, played by Derek Jacobi, into a new incarnation, played by John Simm. Before regenerating, the Master expresses desire to become "young and strong" like the Tenth Doctor. The effect used for the Master's regeneration, though similar to the Eighth, War, Ninth, Tenth, and Eleventh Doctor's, is notably brighter and more colourful, using an array of psychedelic colours. In the following episode, "The Sound of Drums", he indicates that he had been resurrected by the Time Lords to fight in the Time War, thus receiving a completely new lease on life. The Master returns in The End of Time (2009–10), resurrected with the same body he died in, though he makes remarks to suggest that this was not intended. In "Dark Water", the character of Missy (Michelle Gomez) reveals herself to be a new, female incarnation of the Master.

River Song's regenerations

River Song, also known as Melody Pond has regenerated twice throughout the course of the sixth series of Doctor Who. Although she is human and the daughter of Amy Pond (hence her surname) and Rory Williams, she was conceived on their wedding night aboard the TARDIS and therefore was born with genetic traits similar to the Doctor's own race, the Time Lords.

In "Day of the Moon" (2011), Melody Pond as a child (Sydney Wade) walks through a New York City alley at the end of the episode after being shot by Amy in the previous episode. When a vagrant asks of her condition, she explains that all is well, that she is dying, but she can fix it. She subsequently begins to regenerate in the style of the revived series as the vagrant flees in terror.

In "Let's Kill Hitler", it is revealed that she regenerated into a toddler (Maya Glace-Green). This form later matured into Amy Pond's best friend, Mels (Nina Toussaint-White), who regenerated into her more widely known River Song (Alex Kingston) identity after being shot. In the aforementioned episode, post-regeneration, Melody is immune to a barrage of gunfire due to her surplus regenerative energy. In that same episode, River Song used all her remaining regeneration energy to revive the Doctor; as Amy put it "You're safe now. Apparently you used all your remaining regenerations in one go. You shouldn't have done that." She was hospitalised as a result and now no-longer possesses the ability to regenerate.

Other regenerations

In the premiere of the 2009 spin-off series K-9, the original K-9 Mark I (Leeson) is reintroduced and destroyed, but subsequently revealed to have been installed with a "regeneration circuit". At this point, the traditional K-9 model "regenerates" into a more sophisticated-looking CGI model.

In "The Doctor's Daughter" (2008), the Doctor's DNA is used to create the titular "daughter" Jenny (Georgia Moffet), who displays many but not all Time Lord traits. In the episode's close, she is shot in the chest and appears to die. However, long after the Doctor and his companions have departed, she miraculously resurrects and expels energy from her mouth which, ambiguously enough, both resembles regenerative energy and the energy emitted by a planet-restoring plot device in the same episode. The question as to whether this is a true regeneration is left unanswered, since Jenny does not change her appearance.

In "Hell Bent" (2015), while threatened with a gun, the General states to the Doctor that he is currently in his tenth regeneration. The Doctor then shoots him, causing him to regenerate from an old white man into a younger black woman. The General later states that her previous incarnation was her only one as a male.

Visual effects

Each new regeneration was also radically different from the previous one, even in terms of the visual effects used to represent the moment of regeneration. The very first regeneration was devised and executed by vision mixer Shirley Coward, who had rather unexpectedly come up with a method of achieving the effect electronically. The original plan of the production team was simply that William Hartnell would fall to the floor at the end of The Tenth Planet and pull his cape over his face. Troughton would then appear at the top of The Power of the Daleks, retracting the cloak. Coward's then-innovative vision mix necessitated that Troughton be hastily contracted for The Tenth Planet, part four. The series' first regeneration sequence was then duly recorded on 8 October 1966, with the cliffhanger resolution filmed two weeks later on 22 October. (REF: The Second Doctor Handbook) Older portrayals of regenerations were either a simple fade between two incarnations, a glowing effect that revealed the next incarnation, or one incarnation morphing into the next.

Each subsequent regeneration was then filmed in a variety of different ways, as dictated by the director on that particular episode. Indeed, no two regenerations were particularly similar until the Russell T Davies era. Only BBC Wales Doctor Who attempted to standardise the way regeneration looked. Ever since the "The Parting of the Ways", every regeneration has been portrayed as a "golden glow explosion" (although the colour of the explosion is fiery orange in "The Parting of the Ways" and is milky white in Utopia). Rose was the first to describe this type of regenerations, saying "I saw him sort of explode, and then you replaced him" to the Tenth Doctor immediately after the Ninth Doctor regenerated. Also, these regenerations are portrayed as violent discharges that could harm anyone nearby, to the point where the most powerful occurrences, seen in The End of Time and "The Time of the Doctor", were able to destroy the Tardis interior and send out a shockwave that destroyed a Dalek ship along with several troops respectively. Each time there was a regeneration with people nearby, either the Doctor or his companions had everyone present get away from the person who was regenerating to avoid them being harmed. In smaller discharges, regeneration was far less harmful and could be emitted from the hand in wisps of golden regeneration energy, which was capable of healing the injuries of others. The subsequent Children in Need Special established that there was residual "regeneration energy" in a gaseous state after a transformation which had to be expelled through the mouth. This was seen again in "The Christmas Invasion", "The Eleventh Hour" and "The Doctor's Daughter" — though the latter narrative never made quite clear that Jenny actually regenerated. The Tenth Doctor was seen breathing out gaseous regeneration energy shortly after his transformation, as was the Eleventh Doctor. Consciously holding back the regeneration caused a buildup of energy that resulted in a powerful and violent explosive discharge of regeneration energy. Also, gaining a new cycle of regenerations and Time Lords lives being reset resulted in a shockwave and explosion of regeneration energy with the range of a thermonuclear explosion. Directed regeneration energy discharges could destroy anything in its path, even a Dalek Saucer, while the shock wave destroyed any Dalek troops in the vicinity.

This visual standardisation has allowed narratives to play around with regeneration. The mere presence of "regeneration energy" can now be used to heighten dramatic tension. This visual short cut, unavailable to production teams in the classic era, has been a particular favourite of Steven Moffat, who used the "golden glow" liberally throughout the 2011 series; in fact, unlike in the Russell T Davies era, in which nearly every regeneration had subtle differences, every Moffat era regeneration until "The Time of the Doctor" is nearly identical. Several of the 2011 episodes used that VFX in a way that wordlessly suggested regeneration.

See also

• Time Lord physical characteristics

Notes

References

External links

• Rassilon, Omega, and that Other guy: Gallifrey Stuff – every fact about the Time Lords no matter how apocryphal