O'Brian appeared regularly on other programs in the 1950s and 1960s, including "The Nat King Cole Show", "The Jackie Gleason Show", "The Ed Sullivan Show", and "The Dinah Shore Chevy Show", all in 1957. He was seen in Jack Palance's ABC circus drama "The Greatest Show on Earth". He also appeared as a 'guest attorney' in the 1963 "Perry Mason" episode "The Case of the Two-Faced Turn-a-bout" when its star, Raymond Burr, was sidelined for a spell after minor emergency surgery. He served as guest host on episodes of "The Hollywood Palace" in 1964 and the rock music series "Shindig!" in 1965. He was a guest celebrity panelist on the CBS primetime programs "Password" and "What's My Line?" and served as a mystery guest on three occasions on the latter series.