The show's protagonist, the Doctor, has been played by 10 actors over the history of the show so far. The change from one actor to another is written into the plot of the show as regeneration, and the different portrayals are typically treated as distinct characters, to the limit that they have on occasion encountered each other and worked together. The Doctor is currently portrayed by David Tennant, who has commented that he's going to leave the task after appearing in four special episodes throughout 2009 and early 2010.
