The Chuck Stops Here ''Happy Days'' gang will reunite. The entire cast will gather for 30th-anniversary reunion special, including the two actors who played Chuck, Richie's forgotten older brother by Gary Susman. It's one of the enduring mysteries of 1970s TV: What ever happened to Chuck Cunningham? The older brother of Richie and Joanie, he could be seen occasionally during the earliest episodes of Happy Days, usually carrying a basketball. Apparently, the character was such an afterthought that no one noticed when the role was recast, and no one mourned him when he inexplicably vanished from the family after the first season. But now, 30 years later, Chuck Cunningham is finally resurfacing. Chuck will live again in The Happy Days 30, a two-hour reunion special marking the three-decade anniversary of the debut of the 1974-84 ABC sitcom. Variety reports that the special, to be coproduced by Henry ''The Fonz'' Winkler himself, will reunite the entire cast, including Winkler, Ron Howard (Richie), Erin Moran (Joanie), Tom Bosley (Mr. C), Marion Ross (Mrs. C), Anson Williams (Potsie), Don Most (Ralph), Pat Morita (Arnold), Scott Baio (Chachi), Cathy Silvers (Jenny Piccalo), and the two actors who played Chuck: Gavin O'Herlihy and Randolph Roberts. Even Penny Marshall and Cindy Williams, who created the spinoff characters of Laverne and Shirley on Happy Days, will be there. Production begins this weekend with the revival of an off-camera Happy Days tradition, a cast softball game, which will be filmed for the reunion show. ABC hasn't set an airdate for the special, but it could air as soon as November's ratings sweeps period. But what about Al?