Other mistake: When Happy hits the ball in the alligators mouth, he is on the complete other side of the lake where the gator is located, and there is a crowd of people blocking his view, but somehow he can still see through the people and over the lake, to notice the gator taking his ball.Sir William
Other mistake: Speaking to General Hershberg (Michael Moriarty) in his office, Nat Serling (Denzel Washington) implies that it was easily discoverable that the US tank was destroyed by "friendly fire" because the US is the only country which uses "uranium depleted" shells. The correct term is "depleted uranium". Maybe Washington flubbed his lines.
Other mistake: In the scene where Nicole opens her locker and a note from David falls out, the handwriting is exactly the same as the seen where Nicole leaves a note taped to the bedroom door for her father. Although the letters are larger, the same applies to the note on the father's vandalized car, which says he's popped both of their cherries.