In the 80s, during the Showtime Laker dynasty, Magic Johnson, James Worthy, Byron Scott, and A.C. Green used to play in various pickup games in the L.A. area, especially at UCLA. During the time, 50-year-old Wilt Chamberlain was organising and participating in many of the same pickup games.
Wilt and Magic played one particular pickup game on opposing teams, as recounted by the legendary coach Larry Brown. One group featured Wilt Chamberlain playing alongside four UCLA freshman, and the other team had Magic, Worthy, Byron Scott, A.C. Green, and Bernard King.
It was the game point; Magic throws up a Sky Hook, and Wilt blocks it. Magic proceeds to call goaltending while Wilt calls game. Wilt objected strenuously and was supported by Larry Brown, who was the UCLA coach at the time. But Magic persisted. Wilt was pissed off and took this as a personal challenge to block every shot at the rim.
There will be no more layups in this gym. He blocked every shot after that. That's the truth, I saw it. He didn't let one (of Johnson's) shots get to the rim."
Larry Brown, via Game Time
According to Coach Brown, both Magic and Wilt were extremely competitive even in pickup games, especially this one when the score was close. Magic played every pickup game as if it were an NBA playoff game, and Wilt was still in great shape and almost as equally dominant as he was when he was still active in the NBA.
Years meant little to Chamberlain in terms of physical conditioning. He was well into his 50s but remained incredibly strong and active. There are numerous stories about his physical prowess and dominance, and a lot of them by now sound like legends. Still, there is no doubt Wilt was incredibly talented athletically, coordinated, and physically imposing, so this story told by Larry Brown makes sense, and we can definitely imagine it happening.