The Doctor (Doctor Who)
The Doctor is the title character in the long-running BBC science fiction television programme "Doctor Who". Since the show's inception in 1963, the character has been portrayed by thirteen lead actors. In the programme, "the Doctor" is the alias assumed by a centuries-old alien—a Time Lord from the planet Gallifrey—who travels through space and time in the TARDIS, frequently with companions. The transition to each succeeding actor is explained within the show's narrative through the plot device of "regeneration", a biological function of the Time Lord race that allows a change of cellular structure and appearance with recovery following a potentially fatal injury.
Doctor Who (season 21)
The twenty-first season of British science fiction television series "Doctor Who" began on 5 January 1984 with the 5th Doctor (Peter Davison) serial "Warriors of the Deep", and ended with Colin Baker's first serial "The Twin Dilemma". For only the second time (the first being during season 4), the entire TARDIS crew changed over the course of a single season.Peter Davison makes his final regular appearance as the Doctor in "The Caves of Androzani". Colin Baker makes his first full appearance as the Doctor in the final serial "The Twin Dilemma".