Corrected entry: When Zack calls and tells his friend to look up John and Jeremy, all he gives is their fake names, which haven't been used before, and the charity which didn't exist. Therefore there is no way he could have found out everything about them.
Corrected entry: While John and Claire are riding bikes to the beach, towels are seen on the back of the bikes, but once they get to the beach, the towels are gone. When they sit on the beach, they sit in the sand.
Correction: If the towels blew off the bikes, then they would be gone, and they would have to sit in the sand. Since we do not see the towels anymore after this, there is no mistake made.
Corrected entry: When Owen Wilson meets Will Ferrell for the first time, Will has Nunchucks wrapped around his neck. In the next shot when Will sits down in the living room chair, the nunchucks are gone.
Correction: There is a brief period of time between the time Will Ferrell is standing and sitting. He had time to take the Nunchucks off, and you can even hear the Nunchucks hit the floor right before you see Will Ferrell sit down.
Corrected entry: In the scene where all of the guys go hunting, after it shows Owen Wilson and Vince Vaughn talking, in the next shot all of them are in a row and it's panning down. Through the leaves of the tree in the foreground, if you look closely at the trunk of a tree, you can see a mans elbow and part of his head sticking out from beside the trunk.
Correction: The object that is sticking out from the tree is too far away and too blury to be sure what it is. It is possible it can be a branch, something behind the tree. But I played it in slow motion, zoomed and saw nothing that is clearly identified as a mans elbow and head.
Corrected entry: When the Clearly family, John and Jeremy take a trip out on the Clearly family yacht, a close-up shot of Claire shows land in the background and there is no movement. When the shot zooms out again the yacht is shown to be in the middle of the ocean and moving.
Correction: In the close shot she is sitting in front of the boat and the boat is moving but since the land is far away it is hard to notice that. In the following wide shot the land simply isn't close enough for it to be in the shot.
Corrected entry: The tight shot pattern of the shotgun blast to Vince Vaughn's rear end would only be possible at a range that would have caused a severe wound, not just embedded BB's as shown. We won't even go into what actions would be taken towards a member of a shooting party that shot another participant.
Correction: They are hunting quail, so they are obviously using a shotgun shell known as "birdshot". This will not necessarily cause a severe injury to a human, especially in a padded region like the buttocks.
Corrected entry: The first time we see Vince Vaughn and Owen Wilson sitting by Washington Monument, the water in front of them doesn't move at all.
Correction: The reflecting pool in front of the Washington Monument is several hundred feet away. On a calm day, you wouldn't see any waves at that distance.
Corrected entry: When Vince and Owen don't see each other for a long time, that seems to be a stretch since they work in the same office. Vince did not have to put a sign on Owen's home asking where he was, he could have seen him at work.
Correction: It's very possible that he was so depressed that he just stopped coming to work.
Corrected entry: Sack finds out from his friend the true identity of John and Jeremy, but how's that possible? He gives his friend the names John and Jeremy gave him, not their real names. There's no way his friend could've found out who they were without their real names.
Correction: All Sack knew was that they weren't really the Ryan brothers; therefore he assumed, correctly, that they crashed the wedding. Considering the brothers seem to re-use some stories, it's conceivable that his friend found out their story was fake, hunted around, and discovered the truth behind it.
Corrected entry: Zach asks a friend over the phone to hire an investigator to find 'dirt' on John and Jeremy. Later, he exposes them for being Crashers. But since the pair were using fake names, surely all the investigator would have found is that they were lying about their names?
Correction: We don't see how Zach's friend finds out who they really are. There are a lot of ways of finding out information in this day and age.
Corrected entry: When Vince Vaughn is first tackled during the football game, he gets a small grass stain on his sweater right in the middle of his chest. In subsequent shots, the grass stain disappears.
Correction: It is very small spot and it isn't necessarily a grass stain. It could be dirt from the ground that can easily be brushed off.
Correction: Jeremy had confessed everything to the vicar in the scene before. So Zack would have found out that the charity doesn't exist and the vicar may have told everyone about what Jeremy said to him. This point is indicated by Jeremy's line about the vicar telling everyone Jeremy's 'confession'.