 With the public announcement of two Christmas specials and the private knowledge of Billie Piper leaving at the end of Series Two, Davies decided to elevate this story to the Christmas special, not introducing the new companion immediately, and filling the slot with "Tooth and Claw".The end of "Doomsday" is featured as part of the pre-title sequence, although the scene was actually refilmed.In his online podcast commentary for the episode, David Tennant explained that this was due to a change in lighting supervisors, and the one hired for this episode liked to light the TARDIS interior differently; the scene therefore had to be refilmed in order to match.