Deliberate mistake: When Douglas' fingers are chopped off, they are hit from the right side by the blade, but they inexplicably fly directly forward (instead of to the left as they shoot), somersaulting smoothly through the air in a clean, uniform manner. Obviously done for the sake of the 3D effects in the film as they fly directly towards camera, but completely defying the laws of physics.
Deliberate mistake: When Alice jumps from the rooftop, the entire roof explodes, but the wire she is on is still intact. (01:00:50)
Deliberate mistake: When they are playing strip monopoly, Alice purchases Baltic Avenue and then Bill rolls the dice and Alice exclaims that he's rolled an "8" - putting him on Baltic Avenue. However if you look carefully at the dice (before Brenda quickly scoops them up) you can see they show two 5's. (00:40:05)
Deliberate mistake: As Joey is running down the street and having things blow up all around her, you can see other people walking on the sidewalk not reacting to the destruction around them, even when something blows up just a few feet from them.
Deliberate mistake: At the beginning, we see the Scorpion King leading his army into battle. However, despite people being stabbed with swords, and slashed, there is no blood on any of the soldiers, nor on their weapons. Kind of hard to believe war was that clean back then. (00:01:40)
Deliberate mistake: The aliens fire on a bell tower with a clock on it. In the next shot a different building blows up. (01:17:15)
Deliberate mistake: The entire time they spend in the trench, before they attack, Quinn has a white sheepskin jacket. It rains throughout the film yet with all the mud about you would think in about a day that this jacket would turn dark brown. It is still fairly white even when Quinn dies.
Deliberate mistake: When Constantine comes out of the library after speaking with Gabriel, he stands beside Angela and none of them cast any noticeable shadows on the door and walls behind them. When it cuts to a shot above them, shadows are more being cast behind them. This is probably because of different light settings on the set. (00:23:35)
Deliberate mistake: When the saloon patrons pour through the swinging doors in pursuit of Packer, the same people are seen repeatedly. A relatively small number of extras are running around to the rear of the set and re-entering through the back so that they will appear to be a larger crowd of people.
Deliberate mistake: When the teacher walks over the floor towards the blackboard, he walks through a lot of blood. However when it cuts, he leaves no traces of blood where he steps.
Deliberate mistake: When Andy opens the tap to the liquid plastic it is that some of the liquid squirts on his hand. That would hurt and stain, but Andy doesn't seem to care... (01:14:35)
Deliberate mistake: Throughout the movie, Seagal's voice changes. In some scenes, his lines are spoken by someone else (with a much coarser voice) and dubbed in, which is confirmed by numerous sources over the internet.
Deliberate mistake: It is shown throughout the film that card keys are to be used to open the hotel room doors; this is a security measure that is used for doors in elegant and expensive hotels (if not all). There are no hotels that use this measure without having break-safe metal material inside of these doors, yet the killer and cops are shown breaking down doors fairly easily. Add to this the fact that only thin slices of wood are shown breaking off of the doors, not metal nor even the card-keying device.
Deliberate mistake: When the Norwegian starts shooting at the dog, Childs jumps into the snow and you can see the shape before he jumps in where he's had to do this before on different takes. (00:08:40)
Deliberate mistake: In the pitch dark mansion dining room, the approaching zombie's screams are instantly interrupted by silence whenever the flame from Chris' lighter goes out, and then the screams instantly resume when the light returns. While this is obvious artistic license, for the record the level of darkness would have no bearing on whether we can hear the zombie screaming.
Deliberate mistake: The scene where Arnie takes Denis for a high-speed ride was obviously shot in a studio. Arnie throws an empty beer can out of a car doing 80+mph, so the window was rolled down - but his hair isn't ruffled at all. Alternatively, he used concrete as hairspray.
Deliberate mistake: In the scene where we see Bella in her room looking out the window, the months are passing, but she is always wearing the same clothes. (00:28:30)
Deliberate mistake: The opening camera scene, that's supposed to be shot from Michael's POV as a child, is too high as noted that he's almost face to face with his parents at the end of the scene and then is only mid-chest up to the father when he removes the mask. The POV is also too high as he walks across the dining room and as he approaches his sister upstairs.
Deliberate mistake: After Chris gets stuck on the bridge and is trying to restart the van, a shot out the back window shows Jason running towards the van. He is badly limping and holding his knee because Chris just stabbed him in the knee. In the next scene, when Jason is chasing Chris away from the van, and for the remainder of the movie, Jason no longer limps. He walks and runs normally.
Deliberate mistake: Right at the end of the film, the two Norwegians (Lars and Matias) are seen chasing after Lars' dog in a helicopter. Notice how their clothing and the interior of the helicopter are not the same as they looked in the original 1982 film by John Carpenter. It's supposed to be the same event.