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".
Tom Baker
Thomas Stewart Baker (born 20 January 1934) is an English actor. He is best known for his portrayal of the fourth incarnation of the Doctor in the science fiction series "Doctor Who" from 1974 to 1981, a longer tenure than any other actor, and for the narration of the comedy series "Little Britain". Baker's voice, which has been described as "sonorous", was voted the fourth-most recognisable in the UK.