Doctor Who is a British science fiction television programme produced by the BBC. The programme depicts the adventures of a mysterious alien time-traveller known as "the Doctor" who travels through time in his spaceship, the TARDIS, which normally appears from the exterior to be a blue 1950s police box. With his companions, he explores time and space whilst facing a variety of foes and righting wrongs.
The character of the Doctor was initially shrouded in mystery. All that was known about him in the programme's early days was that he was an eccentric alien traveller of great intelligence who battled injustice while exploring time and space in an unreliable old time machine called the TARDIS, an acronym for Time And Relative Dimension(s) In Space. As it appears much larger on the inside than on the outside, the TARDIS has been described by the Third Doctor as "dimensionally transcendental"[43] and, because of a malfunction of its Chameleon Circuit, is stuck in the shape of a 1950s-style British police box.
However, not only did the initially irascible and slightly sinister Doctor quickly mellow into a more compassionate figure, it was eventually revealed that he had been on the run from his own people, the Time Lords of the planet Gallifrey.
As a Time Lord, the Doctor has the ability to regenerate his body when near death. Introduced into the storyline as a way of continuing the series when the writers were faced with the departure of lead actor William Hartnell in 1966, it has continued to be a major element of the series, allowing for the recasting of the lead actor when the need arises. The serial The Deadly Assassin established that a Time Lord can regenerate twelve times, for a total of thirteen incarnations (although at least one Time Lord, the Master, has managed to circumvent this). To date, the Doctor has gone through this process and its resulting after-effects on nine occasions, with each of his incarnations having his own quirks and abilities but otherwise sharing the memories and experience of the previous incarnations:
