The longest running science fiction show Doctor Who has announced as Peter Capaldi as the twelve incarnation of the time traveling alien. Announced on BBC world wide Sunday Capaldi will first appear on screen as the Doctor on the Christmas special this year.
Doctor Who celebrates its 50th year on television this year. The reason the show is able to continue as long as it has with different actors is a plot device known as regeneration. When an actor leaves the Doctor is killed off and then regenerates into the new actor.