Fifteenth Doctor

The Fifteenth Doctor was the Fourteenth Doctor's successor.

A day to come
to be added

A new body
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: )

Other realities
In the Daft Dimension, Ncuti Gatwa was on the cover of an issue of Doctor Who Magazine. (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: )

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 presumably was Fifteen's, owing to the fact that Ncuti Gatwa also played a Ken in the film.