In 1981, Katt was cast as the title role in a filmed version of the Broadway musical comedy Pippin, which received mixed reviews. He won his best remembered role that year, however, as Ralph Hinkley, a mild-mannered schoolteacher given a superpowered suit by aliens on the popular television series The Greatest American Hero, a role he played until the show was canceled in 1983. Also starring veteran actor Robert Culp, the show retains a cult fanbase. Its theme song, "Believe It or Not", penned by Mike Post, also became a hit in the music charts. In 1982, due to the success of the first season of The Greatest American Hero, Katt signed to MCA and released a soft rock album, Secret Smiles under the name Billy Katt.