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".
Paul Marc Davis
Paul Marc Davis (born April 16, 1974) is a British actor who has appeared on "Doctor Who" (the episode "Utopia") and three of its spin-off series: "Torchwood" ("Exit Wounds"), "The Sarah Jane Adventures" (as recurring villain "The Trickster"), and "Class" (as recurring villain Corakinus). This makes him the only actor to appear in all four of the "Doctor Who" series. He was also an executive producer on "Sports Day 3D".