The Enemy Within

The Enemy Within was an alternate title for four different Doctor Who stories, one of them never produced.
 * The Enemy Within was the actual production title of The Android Invasion. It was used on clappers during at least location filming.
 * One of the working titles for The Invisible Enemy was "The Enemy Within". It was referred to as such on the Doctor Who sound effects LP released by the BBC in 1977.
 * The working title for an unproduced storyline by commissioned by John Nathan-Turner and script editor which would have appeared in Season 19. The storyline would have concerned the true source of the power of the TARDIS, an octopus-like creature which subsisted on fear.
 * The Enemy Within was also proposed as a title by producer Philip Segal for the 1996 television movie at a Doctor Who fan convention.