Mason began his film-acting career at age six when director Harold Ramis cast him in Groundhog Day. Three months later, Mason won the title role in the hit comedy, Dennis the Menace. He was chosen from twenty thousand other hopefuls in a nationwide casting call launched by John Hughes and Warner Bros. It was an early and special opportunity to work with the gifted Walter Matthau. Mason has had starring roles in such films at Flatland Pictures' Just in Time directed by Tom Rice; and Morgan Creek's Bad Moon directed by Eric Red, also starring Mariel Hemingway. Among his other film credits, Mason had a wonderful experience working with Leslie Nielsen in Disney's hilarious Spy Hard directed by Rick Friedberg. He also had a role in Gattaca, directed by Andrew Niccol, starring Uma Thurman and Ethan Hawke.