Fifteenth Doctor

The Fifteenth Doctor was an incarnation of the Doctor and the successor to the Fourteenth Doctor. He had at least one adventure involving "Ruby S". (PROSE: )

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

The Twelfth Doctor was forced through seven false regenerations by a "regeneration vampire". With the assistance of the Eleventh Doctor, the regeneration energy he expended was returned to him. (AUDIO: )

Post-regeneration
After an adventure involving "Ruby S", (PROSE: ) the Doctor decided that the attire of his previous incarnation "[wouldn't] do", choosing his new clothing in the TARDIS, sturdy boots and a new hat being amongst the items chosen. (POEM: ) He also wrote in his diary about his adventure, quoting himself saying "what the h[...] here?" (PROSE: )

Further adventures
After the seed of a World Tree landed on Earth on 19 August 1987, the Eleventh Doctor sealed it in a Time Bubble to prevent its exponential growth from destroying the planet, which looped the same day over and over, akin to the plot of Groundhog Day. However, Nora Wicker was inadvertently trapped within the bubble after the Doctor misjudged its size, for forty-six years, so he — using a hard light hologram to enter the bubble transmitted from the moon of Vega — secured the help of a future Doctor to use his sonic screwdriver outside the bubble at the same time he did to create a temporary exit out of the bubble for Nora to escape through. Seconds before the Doctors used their screwdrivers, Nora told the Eleventh Doctor she wanted to remain in the bubble, to accompany the sapient tree, and this caused the Doctor to hesitate, and the sync failed. The Fifteenth Doctor, unable to complete the plan, returned to the TARDIS to return the next day in the loop, however he presumably did not return as to respect Nora's wishes. (AUDIO: )

The Daft Dimension
In the Daft Dimension, the "new Doctor", as mentioned by one fan, was among the exciting new developments of Doctor Who. (COMIC: )

Appearance
The Doctor had a "nice" new face which fitted well into place, with his hair being short and his nose being just right. His legs were firm and his eyes were bright.

Wearing the clothes of their predecessor for a short time and believing them to be "off-the-peg", the Doctor first pondered on wearing a frilly shirt and a scarf before deciding they were "over them" and "a touch too soon" respectively. The Doctor finally chose some sturdy boots, believing them to be handy for the Moon and a "nice" new hat. (POEM: )

The Fourteenth Doctor?
The BBC announcement revealing Ncuti Gatwa's casting as the Doctor was worded ambiguously. Gatwa's Doctor was noted to be the successor to Jodie Whittaker's Thirteenth Doctor, but was only described as "the new Doctor", rather than the Fourteenth Doctor. Nevertheless, numerous news outlets presumed that Gatwa's incarnation would be the Fourteenth Doctor and incorrectly reported as such.

However, Whittaker's final episode, The Power of the Doctor, depicted the Thirteenth Doctor regenerating into a new incarnation once again portrayed by Tenth Doctor actor David Tennant. After Power of the Doctor's broadcast, Russell T Davies confirmed that Tennant's new incarnation was the Fourteenth Doctor, and that Gatwa's would follow as the Fifteenth.

The first black Doctor
The Fifteenth Doctor was the first "main" ordinal incarnation of the Doctor in the programme's history to be played by a black man, namely Rwandan-Scottish actor Ncuti Gatwa; however, other black Doctors have previously appeared in the Doctor Who universe.

Comedian Lenny Henry was the very first non-white actor to portray the Doctor; in an untitled skit from an episode of The Lenny Henry Show broadcast on 3 October 1985, Henry portrayed a parodical Seventh Doctor. Upon Gatwa's casting in 2022, Henry praised the development, noting "a lot of black fans have been looking at our watches for a while! More power to Russell T Davies." While Henry's incarnation is not considered part of Doctor Who's "main continuity", it would take thirty-three more years for a black Doctor to appear in any media.

Russell T Davies's novelisation of Rose, released on 5 April 2018, featured a photograph in conspiracy theorist Clive Finch's possession that showed a tall, bald, black female Doctor who wielded a flaming sword.

The 2020 episode Fugitive of the Judoon introduced the "Fugitive Doctor", a mysterious, previously unknown incarnation of the Doctor portrayed by BAME actor Jo Martin. This unseen incarnation, a predecessor to the First Doctor, joins the ranks of the eight other "pre-Hartnell" Doctors introduced in the 1976 serial The Brain of Morbius. Within the same series as Fugitive, several of the Timeless Children — seven youthful incarnations of the Doctor — were played by BAME child actors, most notably including the first.

In addition, various "bodyswaps" have been depicted wherein the Doctor temporarily possesses the body of a BAME individual, such as Daniel Anthony's Clyde Langer being possessed by the Eleventh Doctor in Death of the Doctor, and Damian Lynch's Benjamin Chikoto, who the Third Doctor uses as a means to communicate in Ghost in the Machine.

At the time of production for Silence in the Library and Forest of the Dead, Steven Moffat secretly intended Doctor Moon to be a future Doctor, meaning that Colin Salmon would have been the first BAME actor to portray a main ordinal Doctor, although this was never revealed in any later work of fiction. In Showrunner Showdown in 2020, Moffat commented that he thought a version of this idea could still work and Russell T Davies revealed that he always thought of the character as the Doctor while watching the episode.

A queer incarnation?
Gatwa has the distinction of being the first queer actor to portray a mainline ordinal incarnation of the Doctor; queer actor Mark Gatiss portrayed an non-ordinal Doctor in the parody skit The Web of Caves, while Geoffrey Bayldon portrayed an alternate universe Doctor in the Doctor Who Unbound audio series.

Though it remains to be seen if the Fifteenth Doctor himself is queer, co-star Neil Patrick Harris has described Gatwa as "the first gay Doctor". The question of which incarnation constitutes the "first gay Doctor" is a matter of debate; the friendship between the Thirteenth Doctor and Yasmin Khan became romantically tinged towards the end of the Chris Chibnall era, though the pair never explicitly expressed their attraction to one another, and the Eighth Doctor was implied to be non-heterosexual in the Eighth Doctor Adventures series of novels. Furthermore, many stories released in the 1990s and beyond reiterate that the Time Lords’ concept of gender differs to that of humanity.

Appearances prior to his first full television story
Continuing the trend set by the Thirteenth and Fourteenth Doctors, the Fifteenth Doctor appeared multiple times in expanded media before his television debut.
 * Interestingly, the Fifteenth Doctor's first appearance was technically before the Thirteenth Doctor's television debut in The Woman Who Fell to Earth; he appeared implicitly in the 2017 poem Contents, as an ambiguous then-future Doctor with short hair, wherein this Doctor rummaged through a chest looking for a new costume, settling on a hat and boots. As revealed on the Official Doctor Who Twitter account, the Fifteenth Doctor does indeed have very short hair, wears a stetson, and boots.
 * His second appearance was also implicitly in the audio drama The World Tree, which, while ambiguous as to which future Doctor appeared in it, Nick Slawicz, the story's author, confirmed that the Fifteenth Doctor was indeed the Doctor present in that story.
 * The pink-painted TARDIS that appeared as part of a cross-promotion exhibit with the 2023 film Barbie could be argued to be that of the Fifteenth Doctor, owing to the fact that Ncuti Gatwa also played a Ken in the film; Russell T Davies claimed the exhibit depicted genuine in-universe events.