Deliberate mistake: When Brad Pitt is in his garage and cleans the spot on this collar, he should have turned the car's mirror to the left to see himself. Instead, he turns the mirror to the right so the camera can get a view of his collar.
Deliberate mistake: In the end of the NASCAR race, Tripp and Gordon get into a crash making Gordon spin, but he somehow is still able to come in second place even though every other racer was right on his back when he spun. He wouldn't have been able to regain that much speed in that short amount of time.
Deliberate mistake: This was probably done intentionally to make them more visible, but the bullet holes left in the stairwell wall by Bart's handgun while he is chasing Danny during the movie's climax look to be about the size of golf balls. Typical handgun calibers aside, just looking at the size of the clip he's loading into the gun and seeing how many rounds it holds, those rounds would have to be much smaller than the holes the bullets made.
Suggested correction: It's a 9mm Glock18. The standard magazines have 17 rounds, the long ones 30. The holes could be larger because it's an old building and the plaster might break apart differently than modern drywall.
Deliberate mistake: With John Cusack leaning to the side to pull Diane Lane and the dog from the water, the rowing scull should have nearly tipped over, yet it leans only slightly. Later in the same scene, the normal instability of such boats can be seen when tipping occurs to a greater degree simply from the dog moving.
Deliberate mistake: The tiny hot air balloon that Francesca released in the debate room would never be able to support Casanova's weight.
Deliberate mistake: During the dance number in the Dead Bar, the blue pirate has a sword stuck through him with the handle in the front, later it changes to the back, then to the front again. Seen when the groom falls back and grabs the handle, then picks the pirate up and drops him. (00:19:15 - 00:20:05)
Deliberate mistake: Frank Beardsley moves his family into an old, defunct lighthouse, and subsequently makes a project of restoring the rotating lamp and actually running it. But lighthouses are navigational devices. Each one in use has its own unique, catalogued period, which identifies it and therefore helps a distant ship determine its own position. By running a "phantom" lighthouse, Frank, a career Coast Guard officer, risks confusing ships' navigators at sea. No real nautical officer would do such a thing.
Deliberate mistake: There was a black wrought iron fence behind Whitney but with enough space for JD to drive between them. After JD parked, Whitney (and her friend) were much closer to the fence, but they were also at the rear of JD's parked SUV, which would not be spatially possible. When JD, Jane, and Ally got out of the SUV, they walked right in front of Whitney, who was now much closer, and the fence was no longer behind Whitney. (00:27:50 - 00:28:14)
Deliberate mistake: In the beginning Chris and Jaime are on the bed talking and she is excited about graduating she is wearing a mini dress. In the shot where she falls face down in his lap and her dress goes up, she's wearing black tights underneath her dress, which are not there in any other shot.
Deliberate mistake: In the ambulance scenes, John Goodman is given oxygen via a nasal tube, probably so he could tell his story. In real life, a mask covering the nose and mouth would be used for maximum effectiveness in such a critical situation.