The Twelfth Doctor is a medical procedure.
`` The Time of the Doctor '' is an episode of the British science fiction television programme Doctor Who , written by Steven Moffat and directed by Jamie Payne , and was broadcast as the ninth Doctor Who Christmas special on 25 December 2013 on BBC One . The Twelfth Doctor is an incarnation of the Doctor , the protagonist of the BBC science fiction television programme Doctor Who . Within the series ' narrative , the Doctor is a time travelling , humanoid alien from a race known as the Time Lords . Capaldi made his first , very brief appearance as the Doctor in the show 's fiftieth anniversary special `` The Day of the Doctor '' ( 2013 ) , as one of the thirteen incarnations of the Doctor who are summoned to save Gallifrey from destruction . In the tenth series of Doctor Who , he is accompanied by two new companions : Nardole ( Matt Lucas ) and Bill Potts ( Pearl Mackie ) .