Revealing mistake: When Thornton and Lou are making the Bruce Springsteen sign, the student at the table is supposed to be writing on a poster but you can see that the marker is not touching the paper.
Revealing mistake: In this film, you can see where the present-day lines on the basketball court have been sanded off and "50's" style lines added.
Revealing mistake: When Paul Newman is playing in the tournament near the end after Tom Cruise humiliates him by dumping the game, Newman lines up to shoot the 2 ball. The point of view shot shows his detailed reflection on the ball's surface. If you look closely at the bottom right side of the ball, you can see that the "reflection" of his shirt exceeds the outside boundary of the ball.
Revealing mistake: When Daniel and Kumiko first see the storm coming near the end of the film, the wind outside is blowing the trees sideways. They open the door to run out and the camera shows what is outside. The trees there are not moving.