On 21 December, a number of things set in or relevant to the Doctor Who universe were released or published.
- 1963 - "The Dead Planet" was first broadcast on BBC tv. Dalekmania began.
- 1964 - Part seven of the comic story The Klepton Parasites was first published in the 680th issue of TV Comic.
- 1965 - The stage play The Curse of the Daleks premièred at Wyndham's Theatre.
- 1968 - Episode eight of The Invasion was first broadcast on BBC1.
- 1968 - Part four of the TV Comic story Jungle of Doom was first published.
- 1974 - Part three of the TV Comic story The Wanderers was first published.
- 1988 - Part two of The Greatest Show In The Galaxy was first broadcast on BBC1.
- 1996 - Part ten of the Radio Times comic story Ascendance was first published.
- 2011 - Part two of Attack of the Snowmen was first published online.
- 2012 - Songtaran Carols was first released online.
- 2014 - Part three of Behind You was first published online.
- 2015 - Part one of Haunted was first published online.