Revealing mistake: When The Mask is dancing with Tina and he turns her into a human tornado while spinning her around, none of the onlookers in the crowd show the slightest bit of amazement at the impossible feat that just occurred in front of them, indicating that the extras were not directed to react to the special effects.Phaneron
Factual error: There are a lot of comments about the Harrier (technically speaking it is an AV-8B, a slightly different aircraft) flown by Arnold Schwarzenegger, but everyone's missed the obvious one. The terrorist with the AK47 is unaware of the fact that a Harrier is hovering just outside the window until he slowly turns and see it there. He does a double take when he sees the Harrier just five metres away! A Harrier is an incredibly loud aircraft; you can hear them from three kilometers away. At that range the floor would shake with the noise and he would have been in no doubt whatever that he had been under attack for some time.
Visible crew/equipment: When Francesco and 'she' are in the cemetery together and the little blue flame-beings gather around to watch them, you can see the wires they're suspended on several times. This is most apparent when Francesco sees the first one (moments before seeing 'she' at the fountain) and also just before they are all frightened away. (00:17:30 - 00:20:40)
Plot hole: In the Cowboys' last possession of the final game, Spike makes a long run before being stopped on the goal line. The Cowboys' next play is a run up the middle. The Little Giants stop the run and the Cowboys lose possession, but since that was the first possession of a new set of downs, the Cowboys would have three more chances to score.
Deliberate mistake: Twice in this film Axel is shot at by multiple gunmen using automatic weapons at close range - and they all miss. In the Earthquake theme ride the bullets ricochet of the rails at Axel's feet. Why are they all aiming low? Why don't they raise their aim? In the park outside he hides behind a perfectly ordinary park bench and the bullets hit the wooden slats. Not one goes through the open spaces between them? I know bad guys can't shoot straight in the movies, but this is ridiculous ...