Answer by
dbusha1 (175)
When Doctor Who premiered in 1963, lead actor William Hartnell was 55. Due to poor health, Hartnell left the show in 1966. The producers, not wanting the popular programme to end abruptly, came upon a unique idea--since the Doctor was an alien being, he could "die" and regenerate as a different person. To date, twelve actors have portrayed the Doctor.