Thirteenth Doctor

The Thirteenth Doctor was the first female incarnation of the Time Lord known as the Doctor and the second incarnation to come from their second regeneration cycle.

A day to come
When encountering the "Vortex Butterfly", the Tenth Doctor was cryptically told that he would not be "limited" to "thirteen lives". (COMIC: Vortex Butterflies)

When the Twelfth Doctor broke his toe, Clara Oswald suggested that he regenerate to heal the injury, but he berated the idea as a waste. (PROSE: The Blood Cell)

When threatened by Captain Lundvik, the Twelfth Doctor told her she would have to shoot him, Clara Oswald and Courtney Woods, but warned that she would "have to spend a lot of time shooting [him] because [he would] keep on regenerating." Clara, during a falling out with the Doctor, later threatened to "smack [him] so hard [he would] regenerate". (TV: Kill the Moon)

While suffering from the common cold, the Twelfth Doctor, overreacting to the illness, considered the possibility of needing to regenerate. (COMIC: The Day at the Doctors)

When the Twelfth Doctor confronted Rassilon in Gallifrey's Drylands after escaping from his confession dial, Rassilon contemplated using his gauntlet to force the Doctor to regenerate as a method of torture, rhetorically wondering how many regenerations the Doctor had been granted, but was interrupted before he could attack the Doctor with the gauntlet. (TV: Hell Bent)

After the Monk invasion, the Twelfth Doctor needed to know if his companion, Bill Potts, was under the control of the Monks, and deceived her into shooting him in a rage to see if she had succumbed to the mind control, secretly putting blanks in all the guns, and faking his regeneration to complete the illusion. He made it look like the process had started, but emerged as himself to show her that he had deceived her. (TV: The Lie of the Land)

After the Twelfth Doctor was captured by and  on a Mondasian colony ship, they debated throwing him off a hospital roof to kill him, but decided against it when they realised their uncertainty on how many regenerations he had remaining, believing they "could have been up and down the stairs all night." (TV: The Doctor Falls)

Regeneration
After the Twelfth Doctor was gravely wounded by the Cybermen on the Mondasian colony ship, the regenerative process began. However, tired of "being someone else", the Doctor delayed the change for several weeks, (TV: The Doctor Falls) until an encounter with his first incarnation, Archibald Hamish Lethbridge-Stewart, and the Testimony caused the Doctor to concede that another regeneration wouldn't "kill anyone". After taking a final look at the universe and providing advice to his next incarnation, the Doctor regenerated inside his TARDIS in an explosive fashion. (TV: Twice Upon a Time)

As they regenerated, the Doctor relived memories from each of their past lives while the Twelfth Doctor's personality continued to give advice. They remembered the magnificence of their TARDIS; (COMIC: The Many Lives of Doctor Who) their first human friends, Ian and Barbara, and a time the First Doctor visited a Pathicol spiritual site with Ian, Barbara, and Susan; (COMIC: The Path of Skulls) the strangeness of some of their adventures, including one the Second Doctor had with Jamie, Ben, and Polly involving living playing cards; (COMIC: Card Conundrum) their love for London, and how the Third Doctor and Sarah Jane saved the city from the Dahensa; (COMIC: Invasion of the Scorpion Men) and their love for parts of Earth outside the UK, such as New York City, where the Fourth Doctor and Romana II retrieved a psychic sales voucher for two Ra'ra'vis. (COMIC: Time Lady of Means)

As she continued the recollections, the Doctor settled into a new body. She next remembered (COMIC: The Many Lives of Doctor Who) Gallifrey and the regeneration limit, and how the Fifth Doctor journeyed into the Cloisters with Nyssa, Tegan, and Turlough and worked with Ophiuchus to break the limit; (COMIC: Ophiuchus) how the Sixth Doctor and Peri saved the Triumvirs from the Haxeen; (COMIC: Virtually Indestructible) the Master, and how the Seventh Doctor and Ace once stopped from murdering Julius Caesar; (COMIC: Crossing the Rubicon) how things weren't always as they appeared, as evidenced during the Eighth Doctor and Josie's rescue of an Omsonii; (COMIC: The Time Ball) and the Last Great Time War, in particular when the War Doctor and Dorium Maldovar destroyed the weapons factories of Villengard. (COMIC: The Whole Thing's Bananas)

With the new incarnation becoming a certainty instead of a possibility, her actualised potential sent postcards with pictures of herself in baggy black clothing to various friends, including V. M. McCrimmon and Grandfather Halfling in the City of the Saved, as a sort of "hello to the world". McCrimmon had letters from two other potential versions of the new incarnation, which were made narratively unstable and destroyed by the postcard. (PROSE: Postscript)

As the regeneration finished, the Doctor noticed that her clothes no longer fitted and felt "there was something different about this body". (PROSE: Twice Upon a Time) After the Twelfth Doctor's ring fell off her finger, (TV: Twice Upon a Time) the Doctor remembered how her ninth incarnation had to relearn to be "the Doctor", and once, with Rose and Jack, saved a Volsci; (COMIC: Return of the Volsci) how the Tenth Doctor, Gabby, and Cindy helped Elizabeth Garrett Anderson become the first female doctor in England; (COMIC: Nurse Who?) her wife River Song and the time the Eleventh Doctor and Alice saved River from Shoalies; (COMIC: Without A Paddle) and, finally, the Daleks, and the Twelfth Doctor and Bill's encounter with a Kaled harvester ship. (COMIC: Harvest of the Daleks)

Still hearing her predecessor in her head, (COMIC: The Many Lives of Doctor Who) the Doctor staggered to the console in a daze. Examining her face in a reflection, the Doctor saw that she had regenerated into a woman, and felt that the change was "brilliant". After she pressed a button on the console, the TARDIS suddenly spiralled into chaos, caused in part by the explosive regeneration. Subsequently, she was thrown out through the TARDIS doors in the confusion after the time rotor exploded, with the TARDIS itself vanishing without the Doctor as she fell towards Earth. (TV: Twice Upon a Time)

New horizons
Sometime after her regeneration, the Doctor stood on a rock overlooking a beautiful ocean during a sunset, as she considered her uncertainty about her future, knowing only that it would be "amazing". (COMIC: The Many Lives of Doctor Who)

Undated events

 * The Doctor once posed as a museum curator in Venice. visited her to ask for the location of items that had been stolen from her in the 14th century. Missy took an old map from her and left. Later, the Doctor saved Antonia from being left behind in 14th century Venice, returning her to the present. She left Antonia with a note chastising Missy for her actions and that she would have to try harder next time. She then cleared out her office and told her assistant to tell anyone who asked that "the Doctor doesn't work here anymore." (PROSE: The Liar, the Glitch and the War Zone)


 * At some point, the Doctor met Cass and gave her a bandolier. (PROSE: The Day of the Doctor)


 * The Doctor had an encounter with Alistair Gordon Lethbridge-Stewart that was recorded on video. (PROSE: Avatars of the Intelligence)


 * At some point before 5 March 2005, the Doctor was photographed "running away from a giant frog in front of Buckingham Palace". (PROSE: Rose)


 * While sitting on a bench in Henry VIII's third-favourite garden, the Doctor thought about the lesson the Moment had wanted to impart. The Moment then joined her on the bench, and when the Doctor asked her why she had helped him the day he saved Gallifrey, she said it was because she did not want to be used. Sometime later, when the Doctor stood in a fountain at the heart of the Villengard banana groves, the Moment appeared again, continuing their conversation. The Moment told her that she helped because the universe had need for the Doctor, and at that point, they was in danger of stopping. Pleased that she finally had an answer, the Doctor went back to the TARDIS with a renewed vigour. (PROSE: The Day of the Doctor)

Personality
The Thirteenth Doctor was not above being secretive and cryptic, handing an annotated map of 14th century Venice, without explaining it and leaving Missy to discover for herself what the annotations meant, while also not divulging her true identity to Missy. (PROSE: The Liar, the Glitch and the War Zone) She demonstrated a playful sense of humour, labelling the Moment's interface "a Christmas cracker", and responding to Cass Fermazzi's mention of having childhood therapy with a dry "[don't] we all". (PROSE: The Day of the Doctor)

The Doctor claimed that she enjoyed making "trip[s] into the past" for research purposes, but knew to be cautious when making such trips. She retained the good nature of her predecessors, making a trip to 14th century Venice to rescue Antonia, and writing a note to chastise Missy for her lack of caution. (PROSE: The Liar, the Glitch and the War Zone)

She retained the guilt demonstrated in her prior incarnations over the events of the Last Great Time War. Visiting Cass prior to her death, the Doctor expressed her regret over Cass' fate and noted that saving Cass was impossible as "[Cass] was too wrapped up in [her] timeline", demonstrating her continued respect for the Laws of Time. She was unwilling to alter her own personal timeline. (PROSE: The Day of the Doctor)

Appearance
The Thirteenth Doctor resembled a woman in her mid-thirties, possessing jaw-length blonde hair with dark roots, and hazel-coloured eyes. (TV: Twice Upon a Time) Lucy Wilson described her as a "beautiful woman". (PROSE: Avatars of the Intelligence)

Clothing
Sometime after her regeneration stabilised, the Thirteenth Doctor took to wearing braces, something that Rose Tyler commented on when shown a photograph of her by Clive Finch (PROSE: Rose) with a light blue trench coat with a hood, dark blue trousers that stopped just over the ankle, blue socks and brown boots. (COMIC: The Many Lives of Doctor Who)

First female Doctor
The Thirteenth Doctor is the first and,, only incarnation of the Doctor in the show's history to be played by a woman. Before Jodie Whittaker, though, the idea of a woman Doctor had been explored.

The idea that a female actor could take the role of the Doctor was first publicly introduced by John Nathan-Turner and Tom Baker in 1980. By Baker's suggestion, he told the press, "I certainly wish my successor luck, whoever he—or she—might be." Peter Davison was cast as the Fifth Doctor, but the idea remained alive, as in a Daily Star article from 29 July 1983, headlined as AFTER Dr WHO... Dr HER?, talking about Davison bowing out, Nathan-Turner said "the hunt for a new doctor starts today and it's quite feasible it will be a woman". Colin Baker was eventually cast as the Sixth Doctor.

In 1986, creator Sydney Newman suggested that "at a later stage Doctor Who should be metamorphosed into a woman", offering Joanna Lumley as the potential candidate for the Seventh Doctor. Frances de la Tour and Dawn French were also mentioned. Eventually, Sylvester McCoy was cast in 1987.

By the time Whittaker was announced as the actor to follow Peter Capaldi, it was well-established, to viewers and within the Doctor Who universe, that the Doctor could be played by a woman.

Though a parody, The Curse of Fatal Death (1999) by Steven Moffat introduced another Thirteenth Doctor, played by Joanna Lumley. This Doctor, upon regenerating, immediately noted that she had "etheric beam locators" (calling back to an earlier gag where etheric beam locators had been confused for breasts). When Emma tells her that those are actual breasts, the Doctor says that she "always wanted to get [her] hands on one of these". At the end, she suddenly finds the Master attractive, and they walk off together, arms around each other's waists.

In 2002, the Big Finish audio Seasons of Fear features the Eighth Doctor telling his future/past enemy Sebastian Grayle, in his own first encounter with that character, that the Doctor is "not a glamorous woman at the moment", hinting that he could become such a thing in the future.

The Big Finish Doctor Who Unbound story Exile (2003), though not set in the prime Doctor Who universe, starred a female Third Doctor, played by Arabella Weir. The story tried to establish that, in this universe, suicide was necessary for a "sex-change regeneration", which was also considered a crime by the Time Lords. Later stories, particularly in the Steven Moffat era, would contradict the idea that changing gender during regeneration was anything out of the ordinary.

Prior to the massive comeback of the TV series in 2005, Jane Tranter wanted the Ninth Doctor to be the first female incarnation, played by Judi Dench.

In 2007, when David Tennant announced his intention to leave, the UK Resource Centre for Women in Science, Engineering and Technology (UKRC) wanted the next Doctor to be female, issuing a statement saying: "There is a distinct lack of role models of female scientists in the media and recent research shows that this contributes to the under-representation of women in the field. The UKRC believes that making a high profile sci-fi character with a following like Doctor Who female would help to raise the profile of women in science and bring the issue of the important contribution women can and should make to science in the public domain."

In 2010, The End of Time: Part Two had the Eleventh Doctor briefly think he had regenerated into a woman, immediately post-regeneration. He quickly realised that he was mistaken, on finding his Adam's apple.

In 2011, Neil Gaiman's The Doctor's Wife was the first to make direct reference to a Time Lord changing gender through regeneration. The Doctor talks of the Corsair, a "fantastic bloke", who was also a "bad girl" in a couple of their incarnations.

In 2013, The Night of the Doctor had the Sisterhood of Karn offer the Eighth Doctor the choice of "man or woman", for his approaching regeneration. However, the novelisation of The Day of the Doctor revealed that the elixir given to the Doctor was just lemonade and dry ice, so the offer is almost rendered a moot point.

That year, the idea of a female Twelfth Doctor gained a media presence. The Guardian offered up their own suggestions for the role.

In 2014, Steven Moffat introduced audiences to, revealed in Dark Water to be the first female incarnation of the Master. Missy was a recurring character in series 8, 9, and 10.

In 2015, Hell Bent showed audiences the regeneration of the General, from a male to a female incarnation. While not the first such regeneration depicted, it was the first to take place on-screen. Just eighteen days before the episode aired, Big Finish audio story The Black Hole had its own male-to-female regeneration scene.

In 2016, Enemy Lines, another Big Finish audio, showed the first female-to-male regeneration.

2017's World Enough and Time included a rooftop conversation, between the Twelfth Doctor and Bill, in which he's only "fairly sure" that his first incarnation was a man, as it was a long time ago. The Twelfth Doctor here claims that Time Lords are "beyond [the] petty human obsession with gender and its associated stereotypes".

The same year, the audio story The Conscript included a conversation between the Eighth Doctor and a Time Lord soldier, where the Doctor stated that he was a "he, for now at least".

Appearances prior to her first full story
The Thirteenth Doctor is unique amongst her previous incarnations by having appeared multiple times in the expanded media before her official television debut.
 * Like most incarnations of the BBC Wales series, she appeared in a specially-made teaser trailer in the run-up to series 11.
 * She was featured in the narrative poem The Death List from the collection Now We Are Six Hundred, with an illustration by Russell T Davies.
 * Postcards from the Thirteenth Doctor to Doctor Who spinoff characters were discussed and depicted in the Lethbridge-Stewart short story When Times Change... (printed with The Two Brigadiers); the Iris Wildthyme short story A Lady Doctor?; and the City of the Saved short story Postscript in Stranger Tales of the City.
 * She was mentioned as appearing with her other incarnations in archive footage during Avatars of Intelligence and Rose.
 * She made an extended speaking cameo in The Liar, the Glitch and the War Zone, though her identity was only revealed at the end of the story.
 * She made a surprise appearance in Chapter 13 of The Day of the Doctor.
 * Her costume made its debut in the invalid comic story And Introducing...
 * The first official trailer featuring this incarnation was put forward as a part of the major press debut of the series 11 team at San Diego Comic-Con 2018.