Deliberate mistake: When the Matoban delegation arrives at the UN, it shows the motorcade entering the circle in front of the UN Secretariat building and stopping at the revolving doors right at the front the staff entrance. Diplomats' motorcades always continue on to the delegates' entrance under a protective tent in front of the GA building so as to allow VIPs to alight from their vehicles to prevent potential snipers from having a view of them. The very next shot of the ambassador shows him riding the escalator, which is at the delegates' entrance, going up to the General Assembly building. This would not have been possible unless they made him walk about 300 meters outside in broad daylight. No chance of that seeing he was already being protested on 2nd avenue all the way from the Queensboro bridge. Obvious reason for this error: The shot of the delegation getting out of the cars looks far better in the open right in front of the UN secretariat building rather than inside a protective tent.
Deliberate mistake: As "Fake Dolly" runs away from Gracie, it is rather obvious in the shot facing Dolly as she runs down the stairs and then when she turns to look behind her, that it really is a fake Dolly running. (00:48:20)
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: When Frank is fighting in the doctors surgery, both he and one of his attackers easily get thrown through walls, yet Lola's shots later don't penetrate to hit Frank when he's hiding in the storage cupboard.
Deliberate mistake: When Amanda is watching the guy cut the skin from the back of his neck, you can see the same shot repeated twice at the beginning and end of the ordeal. It is the zoom in shot of her just as she is about to start shaking her head. (01:16:50)
Deliberate mistake: It's Christmas in Denver and there is snow on the ground. However, there still are quite a fair amount of leaves on the trees in various shots.
Deliberate mistake: It's a really fun visual, but when the bad guys enter the kitchen and get swarmed by African-American waiters in white tuxedos, one can't help but wonder how it could be that Darius was almost the only waiter on the floor up until a moment before - there were a couple others, mostly white dudes, while now we see about 20 people, all of color, coming out at once. The disproportion is huge, it's not like dinner is being served. (00:39:30)
Deliberate mistake: Otis was portrayed as an albino in "House of 1000 Corpses" but in this film he has normal skin pigment.