Wayne Rogers, who played Trapper John in M*A*S*H, turned down the role because he did not want to play a doctor again on television. (He later played a doctor on the television show House Calls, itself a spinoff of a movie, House Calls.)
Pernell Roberts publicly denounced series television when he left Bonanza for theatre in 1965. He decided to return to television because his salary would help support his aging father. He also felt that he would be able to exercise his acting range and address social issues, two things he felt he was rarely able to do on "Bonanza".