In 1961, he moved to Hollywood, where he teamed up with Jerry Belson as a Writer for television. The pair worked on The Dick Van Dyke Show, The Joey Bishop Show, The Danny Thomas Show, and The Lucy Show. Their first television series as creator-producers was Hey, Landlord, which lasted one season (1966–67). Then they adapted Neil Simon's play The Odd Couple for television. On his own, Marshall created Happy Days, Laverne and Shirley (starring his sister Penny), and Mork & Mindy, which were produced by his associates Thomas L. Miller, Robert L. Boyett, and Edward K. Milkis. He was also a co-creator of Makin' It, which the three men also produced.