Revealing mistake: When the cannibal throws Porter's body on the table you can plainly see its a rubber body. Especially when he cuts off the head.
Revealing mistake: In the scene when they are travelling in the RV, the tea in the glass is perfectly still, even when the RV is obviously in motion. The tea should be jiggling in the glass.
Revealing mistake: When serving on the bridge, there are multiple shots where skid marks from previous takes are visible. (00:44:20)
Revealing mistake: When Johnny English tackles the Queen at the end of the film, you can see knee pads worn by the stunt double under her tights.
Revealing mistake: In the scene of the 20th game (the following shot after Brad Pitt leaves the field) we see Jonah Hill looking at him. An extra to the left pulls out his smartphone (which in 2002 was years away from release) and proceeds to take a picture of Jonah Hill.
Revealing mistake: When the LG billboard changes to the blue moon ad, the LG billboard is still visible on a reflection on the glass on the front of the MTV studios building.
Revealing mistake: Near the end of the film when Jamie is 'talking on her phone' in the bathroom you can see in the mirror that she hasn't actually answered it.
Revealing mistake: It's obvious Diaz doesn't actually have a cigarette in her mouth. It looks added in post-production. (00:04:21)
Revealing mistake: Despite her claiming to be topless you can see what looks like a tube top on Kristen Wiig during her attempts to get the state cop to notice her.
Suggested correction: No, she's not wearing a tube-top. Looked up the scene on online. She has her hands covering her nipples, and her passenger Helen has her arm up in a gesturing manner partially covering her breasts, but there's absolutely no tube-top in sight. (I think you may be seeing part of Helen or Wiig's arm and think it's part of a tube-top).
Revealing mistake: After Eddie's big dive, as he resurfaces there is a reflection of the water that can be seen above the waterline (on the camera lens).
Revealing mistake: When Big Momma slips on the table after dancing, for a split second, you can see a single-legged table being pulled with a rope to simulate its breakage, along with a chain visible underneath the table. (00:33:16)