Factual error: Set in the summer of 1977, serial killer David Berkowitz is seen throughout the film wearing a US Army woodland camouflage pattern field jacket. The Army did not start using these jackets nor were any ever made until the early 1980's. They were all solid green until then.
Factual error: Well into the movie, when the cop is searching Adrien Brody for contraband, the cop wouldn't be running his bare, ungloved fingers through Brody's mouth.
Continuity mistake: Warren is shown ripping the locket from Amy's neck after he shoots her, yet when he throws the locket on the seat of the car, the clasp is not broken, as if Warren had removed it properly.
Factual error: When Ryuuichi shoots the man in the car with the shotgun, you see a single large glop of blood hit the windshield. From this range, however, the man's head would splatter all over, not just in the one direction as shown in the movie.
Continuity mistake: At the very beginning of the film we see the Seminar Leader start to write eXistenZ on the board. We see him write the letter 'e', but then the camera changes and he starts to write the letter 'X'. Notice that the letter 'e' has changed from how he originally wrote it. Then when he finishes writing eXistanZ the camera switches position again and the writing has all changed the look again. Most noticeable by the crossing of the letter 't'. As we saw him write it, then cross portion was much higher than in the wider shot.
Visible crew/equipment: When the firetruck arrives you can see the entire crew reflected in the side of the truck.
Continuity mistake: When Hugh Grant is about to propose in the restaurant near the start, his girlfriend's hair keeps moving from in front of her ear to behind and back again with each change of shot.
Continuity mistake: In the scene when Nick Chen (Chow Yun-Fat) talks to Jack (Jon Kit Lee) at the NYC Correction, the shot facing Nick shows him grabing Jack's face by the chin. The next shot, facing Jack, shows Nick's hand around Jack's neck. The final shot facing Nick again shows his hand back on the chin. (00:58:50)
Revealing mistake: When Louie is driving from the mansion, at several times it is obvious that he is not really driving the car. When the car is going straight ahead, he often turns the wheel, and vice versa. This is most obvious just after Vinnie has died, and Louie is asking "Vin? Hey, Vin, you with me over there?". The car is then going through a 90 degree bend in the road, but Louie does not move the steering wheel at all.
Factual error: In a scene in a bar the music playing is Blur's Song 2, which wasn't released until 1998 and a Kula Shaker song which wasn't released until 1996, by which time Nick Leeson was firmly in prison.
Continuity mistake: The whole premise of the movie is a paradox: The main character's colleague thinks the main character has inherited a fortune, and the colleague wants that money which is why he tries to frame him by making him steal some fake drug money. BUT why would the main character run that risk, agreeing to steal the drug money? If he HAD inherited a fortune, he doesn't need a risky ten thousand bucks now, does he? Surely his friend might work out something was up when his supposedly rich friend agreed to run a risk to earn a comparatively small amount?
Factual error: The story takes place in the Pacific Northwest (Vancouver) in November and December. Washington may be known as the "Evergreen State", but there are still numerous deciduous trees - and deciduous trees have leaves that change color in Autumn (yellow, orange, red) and then shed (fall off), not stay green through December or into the new year.
Revealing mistake: When Tsukiko's neighbor has his eyepatch removed, the prosthetic makeup for his scarred face and eye looks incredibly fake and unconvincing, and you can tell his bulging eye is just a painted piece of plastic with fake skin around it.
Deliberate mistake: At about 1 hour 24 minutes, when Tom Sizemore is looking in the mirror, his injured lip goes from original right side to left side.