In 1975, Williams was cast as a fun-loving brewery bottle capper, Shirley Feeney, in an episode of "Happy Days" with Penny, who played her best friend and roommate Laverne De Fazio. The girls were cast as "sure-thing" dates of Richie and Potsie (Anson Williams). Their appearance proved so popular that Garry Marshall, producer of "Happy Days", commissioned a spin-off series for the characters of Shirley and Laverne. Williams continued her role on the very successful "Laverne & Shirley" series from 1976 until 1982. At one point during its run, the series was the number one rated show on television. Williams was praised for her portrayal of Shirley Feeney. She left the show after the second episode of the show's eighth and what would become its final season, after she became pregnant with her first child. The show's various producers were not enthusiastic that Williams was pregnant, as her character Shirley was not pregnant. Williams and co-star Penny Marshall had also been feuding for quite some time on the set long before Williams became pregnant. They would reconcile many years later. The success of the tv series led to a short-lived Saturday morning animated series "Laverne & Shirley in the Army" (1981-82), created by Hanna-Barbera.