Prequel

The Prequels were a series of prologues to certain episodes of Doctor Who from Series 6, 7, 9, and the 50th Anniversary. They were released by the BBC on their official site. They were similar to the Tardisodes produced for Series 2.

Series 6

 * The prequel to The Impossible Astronaut
 * The prequel to The Curse of the Black Spot
 * The prequel to A Good Man Goes to War
 * The prequel to Let's Kill Hitler
 * The prequel to The Wedding of River Song

Series 7

 * The prequel to The Doctor, the Widow and the Wardrobe
 * The prequel to Asylum of the Daleks. A series of webcasts, Pond Life, also acted as a prequel to this story.
 * The Making of the Gunslinger, a prequel to A Town Called Mercy
 * The Snowmen also had two different prequels. The first, The Great Detective, was given a television broadcast as part of the 2012 Children in Need event. The second prequel was released online the following month.
 * The prequel to The Bells of Saint John.
 * Another prequel was released in the build-up to this episode, though it detailed the events which took place just after A Good Man Goes to War and did not directly relate to events or characters from The Bells of Saint John, acting more as another prequel to The Snowmen.
 * She Said, He Said: A Prequel and Clarence and the Whispermen were prequels to the Series 7 finale, The Name of the Doctor.

50th Anniversary

 * The Night of the Doctor and The Last Day were prequels to The Day of the Doctor.

Series 9

 * Prologue was a prequel to the Series 9 premiere.

Home video release

 * The prequels for The Impossible Astronaut, The Curse of the Black Spot, A Good Man Goes to War, Let's Kill Hitler and The Wedding of River Song were released on the Complete Series 6 DVD and Blu-ray box set in November 2011.
 * The prequel for The Doctor, the Widow and the Wardrobe was released on the DVD and Blu-Ray of the story in January 2012, and on the Complete Series 7 DVD and Blu-ray box set in October 2013.
 * The prequels for Asylum of the Daleks and A Town Called Mercy were released on the Series 7: Part 1 DVD and Blu-ray box set in October 2012, and on the Complete Series 7 DVD and Blu-ray box set in October 2013.
 * The prequels for The Snowmen and The Bells of Saint John were released on the Series 7: Part 2 DVD and Blu-ray box set in May 2013, and on the Complete Series 7 DVD and Blu-ray box set in October 2013. Clarence and the Whispermen was also included.
 * The Battle of Demon's Run: Two Days Later and She Said, He Said were released on the Complete Series 7 DVD and Blu-ray box set in October 2013, along with all of the previously released Series 7 prequels.