Third Doctor See List of non-televised Third Doctor stories. Third Doctor The Third Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series "Doctor Who". He was portrayed by actor Jon Pertwee. Within the series' narrative, the Doctor is a centuries-old Time Lord alien from the planet Gallifrey who travels in time and space in his TARDIS, frequently with companions. At the end of life, the Doctor can regenerate his body; as a result, his physical appearance and personality change. Pertwee portrays the third such incarnation, a dapper man of action of stark contrast to his
Doctor Who Doctor's nature, somewhere between the twelfth and final incarnation. On rare occasions, other actors have stood in for the lead. In "The Five Doctors", Richard Hurndall played the First Doctor due to William Hartnell's death in 1975; 34 years later David Bradley similarly replaced Hartnell in "Twice Upon a Time". In "Time and the Rani", Sylvester McCoy briefly played the Sixth Doctor during the regeneration sequence, carrying on as the Seventh. For more information, see the list of actors who have played the Doctor. In other media, the Doctor has been played by various other actors, including Peter Cushing in