There's a rumor that Bewitched was cursed. A lot of cast replacments happened after illness or death, but come on, guys, who would curse an innocent sitcom? Oh, no—we just realized, witches would probably be really insulted that their lives were being mocked.
Dick York suffered from a bad back condition, afer an accident on his film They Came to Cordura, and in the third season his condition caused a number of shooting delays and rewrites. York left the show after collapsing on set and had to be rushed to the hospital, with the rumor he was addicted to painkillers and would regulary black out. Sargent, who played Darren for the next three seasons, was cast the same month. In fact, Bewitched helped coin the popular term "The Other Darrin," which is when a regular cast member is replaced without an explanation to the audience.