Gilliam appeared in the role of "Floyd", the desk clerk in the movie "Paper Moon". He has also appeared in popular motion pictures such as "Blazing Saddles" and "Back to the Future Part III". He has had roles in several other motion pictures such as "Honeymoon in Vegas", "Thunderbolt and Lightfoot", "Farewell, My Lovely", "Fletch", "Gator", "Telefon", and "The Terror Within II". 