Second Doctor
The Second Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series "Doctor Who". He was portrayed by character actor Patrick Troughton.
The Two Doctors
This story marked the final appearance of Patrick Troughton as the Second Doctor and the final on-screen appearance of Frazer Hines as Jamie. The Second Doctor appearing much older in this feature, with noticeable grey hair, has been addressed in novelizations and audio books as there having been a significant amount of time passing between "The War Games" (1969) and the Second Doctor's regeneration in "Spearhead from Space" (1970).