Patrick Troughton
(March 25 1920 – March 28 1987) was the second actor to portray the Doctor. He began his run with The Tenth Planet and finished three years later with The War Games. Troughton's Doctor was quite different than Hartnell's. Troughton brought much more humor and comedy to the role.
In 1966, Doctor Who producer Innes Lloyd decided to replace William Hartnell in the series' lead role. The continued survival of the show depended on audiences accepting another actor in the role, especially given the bold decision that the replacement would not be a Hartnell lookalike or soundalike. Lloyd later stated that Hartnell had approved of the choice, saying, "There's only one man in England who can take over, and that's Patrick Troughton" (Howe, Stammers and Walker, 68). Lloyd chose Troughton because of his extensive and versatile experience as a character actor. After he was cast, Troughton considered various ways to approach the role, to differentiate his portrayal from Hartnell's amiable-yet-tetchy patriarch. Troughton's early thoughts about how he might play the Doctor included a "tough sea captain" and a piratical figure in blackface and a turban. Doctor Who creator Sydney Newman suggested that the Doctor could be a "cosmic hobo" in the mold of Charlie Chaplin, and this was the interpretation eventually chosen (Howe, Stammers and Walker, 68–69).
Regrettably, many of the early episodes in which Troughton appeared were wiped by the BBC. Troughton found Doctor Who's schedule (at this time, 40 to 44 episodes per season) gruelling, and decided to leave the series in 1969, after three years in the role. This decision was also motivated in part by fear of typecasting (Howe, Stammers and Walker, 75; KTEH interview).
Troughton would return to the role in 1973 for The Three Doctors, in 1983 for The Five Doctors, and for the final time in 1985 for The Two Doctors. Troughton continued to work vigorously after Doctor Who despite warnings about his health. Ironically, Troughton passed away in a hotel room while making an appearance at a Doctor Who convention in Chicago in 1987.