Chuck was the eldest Cunningham child, the son of Howard (Tom Bosley) and Marion (Marion Ross), and the older brother of Richie (Ron Howard) and Joanie (Erin Moran). Chuck was a basketball star at Jefferson High but that was rarely factored into any situation on-screen. However, when he was on camera, Chuck was usually holding his basketball, and he was occasionally seen shooting baskets in the Cunningham driveway. A jock with a voracious appetite, Chuck would also be seen in several episodes scarfing down food whenever he wasn't playing ball.
The character only appeared in the pilot episode and 11 subsequent episodes over the first two seasons of "Happy Days" (via IMDb). He went off to college (presumably on a basketball scholarship) during the second season, his character making an appearance in only two episodes. In Season 2, Chuck took a wayward Richie in as a roommate when Richie abruptly left home after a disagreement with his parents, and Chuck was also at the family Christmas later that season. It would be the last time anyone saw him, but fans didn't forget about him.
Chuck disappeared entirely after that episode, and no other mention was ever made of his character ever again. In fact, in Season 11, Howard referred to having only two children, confirming that show writers had moved forward as if Chuck had never existed.
