Doctor Who
Thirteen actors have headlined the series as the Doctor. The transition from one actor to another is written into the plot of the show with the concept of regeneration into a new incarnation, a plot device in which a Time Lord "transforms" into a new body when the current one is too badly harmed to heal normally. Each actor's portrayal is unique, but all represent stages in the life of the same character. Together, they form a single lifetime with a single narrative. The time-travelling feature of the plot means that different incarnations of the Doctor occasionally meet. The Doctor is currently portrayed by Jodie Whittaker, who took on the role after Peter Capaldi's exit in the 2017 Christmas special "Twice Upon a Time".
Doctor Who (2013 specials)
On 1 June 2013, Matt Smith announced that he would be leaving "Doctor Who", with his final episode being the 2013 Christmas Special, with that episode set to feature the Doctor's latest regeneration. Speculation about the identity of the actor set to take over began immediately, with a number of names suggested. The official announcement of the actor of the Twelfth Doctor was made in a special live simulcast on 4 August 2013 in "Doctor Who Live: The Next Doctor", and saw confirmation of Peter Capaldi in the role. The 2013 special is the fourth and final Christmas episode to feature Matt Smith's incarnation of the Doctor, and the second to feature Jenna Coleman as Clara Oswald.