Though primarily known as a writer (and more recently, director), he started out as an actor, in the chorus of
Stephen Sondheim's "Sweeney Todd".
While in "ST", he wrote a musical ("Marry Me a Little") utilizing Sondheim's songs, in which Lucas co-starred. The legendary Sondheim frankly told him he should be a writer instead of a performer, and Lucas has gone on to become one of the most prolific and acclaimed writers of his generation.