Dick York As Darrin Stephens In "Bewitched", Replaced By Dick Sargent
Richard York had a severe back ailment from an incident in 1959 that he got while working a set. In 1969, when Daddy Does His Thing was under production, Richard passed out and was taken to the hospital. Shortly after, Richard Sargent got cast in the show, and left the show shortly after.
Also, how would anyone be able to tell when some background character in GoT was replaced? There were a ton of them, and they all looked the same.