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 scene where Trout's gang burns the school and kills Sam, there is a part where Katherine runs into the sheriff's office then exits. A few seconds later, Katherine runs by a shop on which the name is reversed. Very obvious. (00:51:40)
Revealing mistake: During the close-up of the gas canisters, the condensation is running upwards and "into" the valve. (01:31:10)
Revealing mistake: When Casper is pulled through the window with zombies hacking and chewing on her legs, her stumps end up as two clean cuts.
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: 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 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: 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)