Two NBA superstars and a movie star walk into a high school gym ...
Here's Dwyane Wade and Jimmy Butler enjoying their day off at a local Illinois high school hoops tournament Tuesday afternoon ... along with Wade's wife, Gabrielle Union.
The trio attended the Pekin Insurance Holiday Tournament -- a 3-day competition between some of the area's top talent.
Unclear why they were there .. but witnesses say they seemed to be having a great time and all 3 signed autographs after the game.
As for the game .