[2] In "The Day of the Doctor", Smith and Coleman star alongside David Tennant and Billie Piper; Tennant reprised his role as the Tenth Doctor, while Piper, although credited as playing Rose Tyler, in fact portrays a manifestation of "The Moment", a Gallifreyan super-weapon, that has taken on Rose's form.

[7] On 8 April 2013, the BBC announced that Jemma Redgrave would reprise her role as Brigadier Lethbridge-Stewart's daughter Kate Stewart from "The Power of Three".

It's been a long game, but most of the questions that people ask will be answered... Moffat was developing ideas for the 50th anniversary episode as early as late 2011, when he stated that the team "knew what [they] want[ed] to do" and were "revving up" for the episode in an interview discussing his work on the 2011 film The Adventures of Tintin,[19] and began writing the script for "The Day of the Doctor" in late 2012, announcing that, as a security precaution, he had not produced any copies, instead keeping it on his computer until it was needed.

In September 2013, it was revealed that the Cybermen would feature in the Christmas episode, when one of the show's regular stunt artists tweeted that she would be playing a Cyberman.

On 2 April 2013 filming of "The Day of the Doctor" began, with David Tennant, Billie Piper, John Hurt and Joanna Page seen at a location outside Neath in South Wales.

[27] At the 2013 Comic-Con, Matt Smith confirmed that production of the Christmas episode would begin in September, once his work on How to Catch a Monster was complete.

On 10 September, Matt Smith and Jenna Coleman were seen filming on location at Lydstep Flats in Cardiff, which have previously been used in Series 1 and 2 as the Powell Estate where Rose Tyler lived with her mother Jackie.

[40] In addition to the 50th anniversary episode featuring Matt Smith and David Tennant, a further special was produced to celebrate Doctor Who's half-century.

An Adventure in Space and Time, written by Mark Gatiss, was a feature-length docudrama detailing the conception and initial production of Doctor Who.

[41] It featured David Bradley as William Hartnell and Reece Shearsmith as Patrick Troughton; Matt Smith has a cameo as himself in his Eleventh Doctor costume.

[48] In October, Big Finish Productions released a 50th anniversary special audio drama featuring the Fourth through Eighth Doctors entitled The Light at the End.

[82] Ben Lawrence of The Daily Telegraph gave "The Day of the Doctor" five stars, calling it "charming, eccentric and very, very British.

"[85] Den of Geek's Simon Brew praised the special, calling it "terrific", and stating that it was "pulsating with comedy, ambition, and top to bottom entertainment.

He wrote that Steven Moffat had "performed the fourth remix of the show's mythology in a row, tying up strands that date back to the beginning of Matt Smith's run."

"[88] Mark Snow of IGN gave the episode a score of 8.4, "GREAT", writing that "'The Time of the Doctor' was an exemplary exercise in celebrating the departure of a loved one.

While criticising its "rapid, almost breathless pace", he concluded, "It was a melancholic yet ultimately merry end to one of the show's best Doctors to date.