The Second Doctor

When William Hartnell was forced to leave Doctor Who due to ill health, it was decided that because the Doctor was an alien he might be able to change his appearance when the need arose. Exhausted by the adventure with the Cybermen in The Tenth Planet, the Doctor went through "renewal" (the term "regeneration" was not introduced until later), and Patrick Troughton took over between 1966 and 1969, during Seasons 4 to 6. Troughton reprised the role for the 10th anniversary story The Three Doctors (1973), the 20th anniversary story The Five Doctors (1983), and the Season 22 serial The Two Doctors (1985). He died in 1987.

Seasons

SEASON 4 (1966-67)

SEASON 5 (1967-68)

SEASON 6 (1968-69)

Other Appearances

SEASON 10: The Three Doctors (1972-73)	SPECIAL: The Five Doctors (1983)	SPECIAL: Children in Need (1985)
SEASON 22: The Two Doctors (1985)