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
The serial format changed for the 2005 revival, with a series usually consisting of thirteen 45-minute, self-contained episodes (60 minutes with adverts, on overseas commercial channels), and an extended 60-minute episode broadcast on Christmas Day. This system was shortened to twelve episodes and one Christmas special following the revival's eighth series, and ten episodes from the eleventh series. Each series includes both standalone and multiple episodic stories, linked with a loose story arc that is resolved in the series finale. As in the early "classic" era, each episode, whether standalone or part of a larger story, has its own title. Occasionally, regular-series episodes will exceed the 45-minute run time; notably, the episodes "Journey's End" from 2008 and "The Eleventh Hour" from 2010 exceeded an hour in length.