Deliberate mistake: When Elliott and ET are on the bike heading to the forest on Halloween night, ET is covered with the white sheet, but in the closeup of ET's face right before the bike flies he's covered with the white blanket (note the material), which is from the scene later in the movie.
Deliberate mistake: When Jen Moo and Ching fling back the fire bombs thrown by Leong Kit, they set the rear ends of his students on fire. But since they were all standing facing front and dispersed around the altar, they would be most unlikely to be hit that accurately in that particular place.
Deliberate mistake: The text the Master Control Program speaks in the human world is usually accompanied with a text projected on a computer screen. When Flynn attempts to hack into the system through the laser lab terminal, the Program is cut short at 'I'm afraid you.' (both on the screen and in speech) as Flynn progresses. In reality, however, it should be that the full text intended to be relayed by the MCP should be displayed on the screen, and only the speech gets interrupted. (00:29:40)
Deliberate mistake: When the security forces arrive at the hangar to report seeing Gant at security gate 3, they are driving an American Jeep.
Deliberate mistake: When women are being shown naked by the x-ray machine, they look wrong. If the machine just sees through clothes, their breasts wouldn't look normal, but squashed together and supported by a bra.
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: When the girls are done snorting the "coke" and Rick takes the tray away, none of the girls have snorted any of it because the same amount is still there except instead of lines it is now all muddled together. Also if you watch closely when they are snorting the coke, the rolled up bill only gets close to their nostril and not partially inside it. (00:09:45)
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.