Season 20

Harry Morgan (aka Colonel Potter from M*A*S*H) as ? in "The Wiving"

Episode 20

Gary Busey as Harve Daley in "The Busters"

Episode 23

Robert Urich (aka Spenser) as Manolo Etchahoun in "Manolo"

Episode 24

Victor French as Dibble Pugh (aka Isaiah Edwards from Little House on the Prairie) and Bruce Boxleitner as Toby Hogue (aka Lee Stetson from Scarecrow and Mrs. King) in the last episode, "The Sharecroppers".