Harry Potter

Published in the late 20th and early 21st centuries, Harry Potter was a series of novels originated by the British author J.K. Rowling.

The Doctor was familiar with them as early as his first incarnation. (PROSE: A Big Hand for the Doctor) By his tenth incarnation, the Doctor had read the seventh Harry Potter novel, and cried upon reading the ending. (TV: The Shakespeare Code)

There were ten novels, starting with Harry Potter and the Philosopher's Stone. The Eighth Doctor had a complete set in his TARDIS. (PROSE: The Gallifrey Chronicles)

A copy of Harry Potter and the Philosopher's Stone was in a display case on Platform One. (TV: The End of the World) A descendant of Rowling known as PQ Rowling wrote Harry Potter and the Half-Moon Dentist. (PROSE: Doctor Who and the Adaptation of Death)

Behind the scenes

 * In real life, only seven Harry Potter novels (plus several spin-off works) have been published.
 * Martha's use of Expelliarmus comes from the actual works (it's the incantation for the Disarming Charm, introduced in Chamber of Secrets and used throughout.)
 * The mention of Harry and Ron taking a flying car to Hogwarts also references canon, as the two of them took Mr Weasley's enchanted Ford Anglia to Hogwarts in Chamber of Secrets.
 * In 2005, Russell T Davies asked Harry Potter's creator J.K. Rowling if she would write for Doctor Who. She refused, saying that she was "amused by the suggestion but simply doesn't have the time." She was writing the sixth Harry Potter novel (Half-Blood Prince) at the time.
 * In The Christmas Invasion, as the Doctor considers what clothes to wear in his new incarnation, a uniform with wizards' robes, similar to the way Hogwarts uniforms were presented in the Warner Bros. film adaptations of the Harry Potter may briefly be glimpsed.
 * The Shakespeare Code, in which the Doctor references reading the seventh book, was broadcast before Deathly Hallows was published and during a period of intense anticipation of its release. The Doctor doesn't mention the book's title, as it had not been revealed by the time the episode began filming. The fact the Doctor was emotional about the book's ending was an educated guess on behalf of the script writer that the conclusion to the long-running book series would be an emotional event.
 * According to the book The Writer's Tale by Russell T Davies and Benjamin Cook, Davies also considered basing the 2008 Christmas special around an appearance by Rowling.
 * When filming the 2005 series Russell T Davies commented upon the difficulty of finding little person actors for Doctor Who because Harry Potter and Charlie and the Chocolate Factory were filming at the same time.
 * Both franchises are featured together in LEGO Dimensions, as is ''Harry Potters spin-off franchise '.

Shared actors and connections

 * Harry Melling, who plays Dudley Dursley (Harry's cousin) in the film series, is the grandson of Patrick Troughton. However, he never met him, as Patrick died before he was born. David Troughton is his uncle. Melling himself would later have a role in the Big Finish Doctor Who audio story The Whispering Forest.
 * Alfie Enoch, who plays Harry's friend and dorm-mate Dean Thomas, is the son of William Russell. (After the Potter series ended, Enoch adjusted his name to Alfred Enoch as he launched a TV acting career in the US.)
 * David Tennant is, just like the Tenth Doctor, a huge fan of the Harry Potter series. Tennant appeared in  as Death Eater Roger Lloyd Pack appeared in the same movie as the father of David's character. Coincidentally, Goblet of Fire, which includes Alastor "Mad-Eye" Moody morphing into Crouch, opened in British cinemas the same day that Tennant made his first appearance in earnest as the Tenth Doctor in the Children in Need Special minisode, which is set immediately after regeneration.
 * The Twelfth Doctor briefly communicated with Eddie Redmayne, who was in costume as his Fantastic Beasts character Newt Scamander, in Looking for Pudsey, which first broadcast on the day the aforementioned film was released. Redmayne also voiced Newt in LEGO Dimensions.
 * Outside of the films, the series also had a stage play sequel titled Harry Potter and the Cursed Child. In the original West End production, Noma Dumezweni portrayed Hermione Granger (played by in the films).
 * Stephen Fry recited the UK releases of the audio books.
 * Other actors who have appeared in the Harry Potter film series include, but are nowhere near limited to, Michael Gambon, Warwick Davis, Mark Williams, Zoë Wanamaker, David Bradley, Miriam Margolyes, and Toby Jones.