In the 1950s, Cady played Doc Williams in Ozzie and Harriet (1953–64). In 1961, he made a guest appearance on Perry Mason as twin brothers Joe and Hiram Widlock in "The Case of the Pathetic Patient". He was prolific in television and was the only actor to play a recurring character on three television sitcoms at the same time, which he did from 1968 to 1969, appearing on The Beverly Hillbillies, Green Acres, and Petticoat Junction simultaneously. As Sam Drucker, he appeared in 142 of 170 Green Acres episodes during its six-year run from 1965–71. Also as Sam Drucker, he was one of only three co-stars of Petticoat Junction who stayed with the series for its entire seven-year run (1963–70), along with Edgar Buchanan and Linda Henning, appearing in 152 of the show's 222 episodes. He played Sam in 10 episodes of The Beverly Hillbillies in 1968–70, and he continued his Sam Drucker role in the final season of Green Acres after Petticoat Junction ended in 1970.