List of supplementary Doctor Who episodes

"Doctor Who" is a British science fiction television programme produced by the BBC. The show has been a large influence in the media since its inception in 1963. Running parallel to its parenting seasons and series' lie miscellaneous television broadcasts, several episodes into home video "exclusive" releases and many video games. This list does not include adverts or skits from other shows (bar crossovers and stories as part of telethons i.e. CIN).
Television broadcasts.
There have been several special "Doctor Who" episodes and serials that are produced by the BBC. They usually consist of minisodes, crossovers with other TV shows, and stories produced for special occasions.
Internet broadcasts.
There have been several special "Doctor Who" internet broadcasts.
Prequels.
Throughout the sixth and seventh series beginning with "The Impossible Astronaut", several prequels were released online, which acted as openers for their accompanying episodes. All "prequels" were released ahead of their accompanying episodes, with the exception of "Battle of Demons Run - Two Days Later" which was released after "The Snowmen". The concept is similar to that of the second series, in which each episode had an accompanying Tardisode. In August 2013, a prequel to "Deep Breath" was shown in cinemas prior to the debut of the episode. Two prequels to the ninth series premiere, "The Magician's Apprentice", were released in September 2015. The following year another prequel came out introducing the Doctor's companion Bill Potts. Stories from the original run have also had new scenes and prequels, such as "The Evil of the Daleks", which gained an extra prologue for its rebroadcast the following year, as did "The Crusade" for its 1999 VHS box set release.
Parodic sketches.
There have been several special "Doctor Who" parodic sketches either on television, online or on DVD.