As the cantankerous and cynical Carlin, Riley played one of psychiatrist Bob Hartley's (Bob Newhart) most frequent patients. In addition to appearing on The Bob Newhart Show, Riley also supplied the voice for Stu Pickles on the animated program Rugrats.
Riley's other TV credits include Night Court, Diff'rent Strokes, Seinfeld and Friends. He also appeared in several Mel Brooks films, including Spaceballs! and History of the World: Part I.