The BBC's Doctor Who grew a large fanbase after its 1963 release, but after three years it became clear that William Hartnell, the original actor, needed to leave the series due to his poor health. Rather than end the show with Hartnell's departure, producers leaned into the character's alien nature and just recast the role in 1966 with Patrick Troughton, whose portrayal helped establish many of the hero's unique qualities. However, after three years Troughton also left the role behind -- but for very different reasons than Hartnell.

Hartnell himself suggested Troughton for the Doctor, a choice that producers happily got behind. His experience as a character actor suggested not only a versatility but also a way to differentiate this Second Doctor from the character's original appearance. Troughton's Second Doctor was more light-hearted than the First Doctor. His scruffy appearance and bumbling demeanor, however, hid a firmer side and a penchant for manipulation. The oversized coat, safety-pinned bow-tie and stovepipe hat also helped give the Second Doctor a disarming appearance and highlight his differences from his predecessor.

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Doctor Who Troughton TARDIS

After three years in the role of the Doctor, Troughton left the show. The famously grueling role had taken its toll on Troughton -- although the production schedule and show lengths were different in Doctor Who's first incarnation, Troughton was filming more than 40 episodes a year. Troughton also told KTEH that he was also afraid of being typecast and losing out on future roles if he stayed on Doctor Who much longer.

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Troughton's departure set the stage for many of the Doctors that came after him. Not only did the three-year limit become unofficially standard, with Troughton advising Fifth Doctor Peter Davison to take his leave then, but so did the demanding nature of the role. Many of the later Doctors' actors have cited similar reasons for their departure from the show. Other sources, however, have claimed that Troughton's departure also coincided with a drop in popularity, with the BBC eager to reinvent the role to keep Doctor Who going.

Doctor Who's Second Doctor helped to set the tone of the series. With a second actor playing the titular role, the Doctor's alien-ness became even clearer and the pattern for later season regenerations was established. Troughton's character actor-informed portrayal of the Doctor also solidified the idea that each version of the character would be drastically different from what came before. Troughton brought to Doctor Who an idea of what makes the Doctor unique -- and also when it was time to say goodbye.

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