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.
The Doctor (Doctor Who)
Russell T Davies has expressed a dislike for stories in which multiple incarnations of the Doctor meet, stating that he believes they focus more on the actors than on the story itself. In 2007, David Tennant showed enthusiasm for the idea of a multi-Doctor story, but expressed doubts about the practicality of episodes involving multiple previous Doctors, given that three of the actors who played the character were deceased.