Appearences:EditThe Twelfth Doctor makes a first (and uncredited) appearance in the programme's fiftieth anniversary special, "The Day of the Doctor", when thirteen incarnations of the Doctor unite to save his home planet of Gallifrey from destruction during the Time War. At first, Time Lords in Gallifrey's war room spot twelve blue TARDISes approaching and encircling the planet. This count is then corrected to thirteen, and Capaldi's hands, eyes, and forehead are fleetingly shown. The Twelfth Doctor then makes his full debut at the end of the next episode, "The Time of the Doctor", after the Eleventh Doctor, about to die from old age, is remotely given a new regeneration cycle from the Time Lords, who remain hidden in a pocket universe. He is set to return in "Deep Breath", the first episode of the eighth series.
Matt Smith, who played the Eleventh Doctor, announced his departure from Doctor Who on 1 June 2013. Prior to the revelation of Capaldi as the next Doctor, there was extensive media speculation on the subject.On 3 August 2013, bookmakers William Hill suspended betting when Capaldi became the five to six favourite to be cast. Capaldi's casting was revealed on 4 August during a live broadcast on BBC One, titled Doctor Who Live: The Next Doctor. The live show was watched by an average of 6.27 million in the UK, and was also simulcast in the United States, Canada and Australia. While Capaldi was the first choice for the role, other actors were also approached in case Capaldi should turn the offer down. Ben Daniels, who was an early favourite following the announcement of Matt Smith's departure, said that he had been approached with a view to assessing whether he would be interested in playing the Doctor, with his name remaining as a potential contender until just before the live BBC broadcast. Doctor Who head writer and executive producer Steven Moffat said that Capaldi "briefly flicked through [his] mind" while casting the Eleventh Doctor, but that he dismissed the idea, thinking he was not right for the part at the time. Ben Stephenson, the BBC's drama commissioner, said that Capaldi was suggested months before the August revelation and that a secret audition was held at Moffat's home. Capaldi prepared for the audition by downloading old Doctor Who scripts from the Internet and practising in front of a mirror. He discovered he had been given the part during filming for Adrian Hodges' The Musketeers in Prague; after missing a call from his agent, Capaldi rang back to be greeted with "Hello, Doctor!" At 55 years old when originally cast, Capaldi is almost the same age as William Hartnell (the First Doctor) when he was cast in the role (with Hartnell having been only a few months older than Capaldi was when he was cast for the role), and will be the oldest actor since Hartnell to star in the show. Moffat felt that an older actor would work best following the youngest actor, as it would both provide a change and lessen comparisons. He commented, "I can absolutely believe that the strange old-young Matt Smith will turn into the strange young-old Peter Capaldi." Capaldi has previously appeared playing other roles in the Doctor Who franchise. He portrayed Lucius Caecilius Iucundus in the 2008 episode "The Fires of Pompeii" and John Frobisher in Children of Earth, the 2009 serial of the Doctor Who spin-off Torchwood. Moffat has stated that he plans on explaining over time why there are three characters in the Doctor Who universe with the same appearance; his predecessor Russell T Davies had once explained to him a theory for the first two, and upon Capaldi's casting assured Moffat that the explanation would still work.Capaldi's casting marks the second time an actor has previously appeared in the series and then been cast as an incarnation of the Doctor, the first being Colin Baker. Capaldi briefly appears in the 50th anniversary special. Moffat stated that it was his "plan from the start" that all the Doctors would fly in to save Gallifrey, and he knew there would be a new one at that time. He wrote it before knowing who would be cast.Capaldi filmed his appearance on 3 October 2013, long after principal photography for the special had ended, and the same day he filmed his debut scene for "The Time of the Doctor"