Answer
Conrad Bain is most famous for portraying patriarch roles in three iconic sitcoms. He became a household name through his portrayal of Phillip Drummond in "Diff'rent Strokes" from 1978 to 1986. Prior to that, he enjoyed success as Dr. Arthur Harmon in "Maude" from 1972 to 1978. In between these two shows, he portrayed Stanley Roper in the popular sitcom "Three's Company" from 1977 to 1979.