6. William Hartnell from Doctor Who
This particular Doctor from the hit show Doctor Who had to leave the show because his health was declining and arteriosclerosis. He found out that he could no longer keep up with the demanding schedule of acting and he had to drop out. Because the show was doing so good, the producers came up with the idea that the Doctors could regenerate themselves into a new body. So that’s how the whole concept came up huh?