Revealing mistake: When Ali is in the rain on the pay phone at the motel it is a modern phone, not from the era they were trying to portray.
Revealing mistake: During the limo ride to the hotel, the gearshift of John Cusack's limo can be seen in the park position every time they show his driver, even before they pull over to decide who will arrive first.
Revealing mistake: When Corky (as Agent Pissant) is taking the perp in and starts to sing, the car makes a full 90° left turn (you can tell by the background), yet he never turns the wheel and both hands stay on the top of the wheel.
Revealing mistake: When the group comes across the first ass-blaster, it hops out from behind the fence. Pay attention to its right leg when it jumps out and you'll see a rock on the ground just appear behind it. After it spots them, it stomps a few times. While it's stomping, pay close attention to the rock and you'll see it and some of the ground around it just disappear after a few frames. This rock also isn't visible in any other part of the scene. (01:01:10)
Revealing mistake: At the start, when the girls in the bunk are standing in front of the mirror, the first shot of them looks as if the camera is facing the mirror and we're seeing their reflection, but note that neither the buttons on Alexa's blouse nor her white bracelet are on the opposite side. The "mirror" is actually regular glass with the girls standing behind the glass to mimic a reflection, though Alexa's blouse and bracelet reveal the secret. (00:03:05)
Revealing mistake: In the intro (or one of the intros, rather), they narrate Pootie Tang's origin. A fake newspaper called "New York Pone" is shown, with the front page dedicated to baby Pootie and his invention of a new language. All fun and everything, but the prop is sloppy; you can read below the name of this fake 70s newspaper the URL of the New York Post' s website and the date in April 2001. (00:08:35)
Revealing mistake: When Professor Oak is getting a book from a bookshelf, the book appears out of nowhere. (01:15:52)
Revealing mistake: The tentacle slaps the Captain, but he's already got the wound.
Revealing mistake: Despite playing a blind character Helen Slater is noticeable when she appears to be using her sight throughout the movie.
Revealing mistake: Grandma handles the remote control in clumsy fashion, sending the model helicopter too close to the buffet and ruining the party. That's the idea at least; in truth, the cakes are catapulted in the air by devices placed under them. They are easy to spot because of the wrong timing, the geyser-like puffs of smoke they create, and you can even see marks at the bottom of a tray. (00:07:30)