Revealing mistake: When John Cusack is driving the actress, there is a shot looking over his right shoulder at the dashboard. The speedometer reads 0 mph. (00:08:15)
Revealing mistake: When Sean Penn is in the funeral home looking at his daughter's body, when he lays the dress over her the rise and fall of the very alive actress' chest is visible as she breathes. (01:07:40)
Revealing mistake: In the overhead view of the bus driving across the desert to Camp Greenlake the dust behind the bus is CG, and near the end of the scene the bus moves up in the frame and the end of the dust trail cuts off with a straight line.
Revealing mistake: During the close-up of the gas canisters, the condensation is running upwards and "into" the valve. (01:31:10)
Revealing mistake: In several scenes of the zombies swimming under water, they are obviously holding their breath. Would a dead zombie need to do that?
Revealing mistake: When Robert Downey Jr. is taking Halle Berry's blood pressure, the needle doesn't move as he pumps the hand inflator.
Revealing mistake: When Dae-su enters the room of one of his nemesis, his computer screen shows information about the stock exchange. The Internet address on the screen is: C:/DocumentsandSettings/[.]/OldBoy/[.], which would be a link to a folder on that computer, not an Internet address.
Revealing mistake: In one of the flashback scenes at the "bunker", a number of the shots fired pierce the sheet metal roof. When they show these holes, you can see fairly bright light coming through. This scene was supposed to be in the jungle during the night. There shouldn't be light streaming in; moonlight is not that bright. It was obviously artificial light used to enhance the scene.
Revealing mistake: When young Ichi has a "climax" at the end, you can tell his "spunk" is really just white goop and isn't real.
Revealing mistake: In 1981, when most of the story takes place, the 1981 Dodge Diplomat was the most common police cruiser, but the director of this film chose the 1987 Chevy Caprice Classic.
Revealing mistake: After the assembly where Grace speaks to the Dogville people she walks home chained to her wheel. However, the wheel that's supposed to be so heavy that she can hardly move around gets pulled along with the chain hanging through a little. (02:05:10)
Revealing mistake: When Frank yells stop to Marion, you can see the marks on the road from a previous take. (01:05:20)