Continuity mistake: In the dinner scene where Derek is over, he is telling a story to Robert about fishing. During the whole scene if you watch Alice who is sitting beside Derek, her wine glass repeatedly jumps from her hands to back on the table instantly. (00:24:50)
Continuity mistake: When Dale is questioning Brennan as to why he is sweaty, and again when he comes downstairs after examining his drum kit, the remote control Brennan has swaps which hand it is in a few times and his hands keep switching their position too. (00:16:45)
Continuity mistake: When Brennan and Dale are watching TV, there's a blue can of Pepsi on a table, but in the next shot the blue can disappears from the table.
Continuity mistake: After arriving to the new house, Brennan is seen in the car as Nancy and Robert talk to the neighbor (Don). Brennan's arm is seen up holding the handle on the interior of the car near the window then down between each shot. (00:06:05)
Visible crew/equipment: When Brennan and Dale are on the stage at the wine mixer, Brennan sings opera and when Dale plays the drums you can see a crewmember reflected underneath the cymbal.
Continuity mistake: In the scene with the bullies, as the bullies are approaching and one says, "Hey, fag stick," Dale and Brennan are stationary next to a tree. When he says,"Long time no see," they are moving to the same position again.
Visible crew/equipment: After their argument in the car (after Brennan and Dale have shown their presentation), Robert rushes into the house. As the camera moves backwards, you can see a crew member reflected in the mirror on the wall. (00:57:10)
Continuity mistake: When being attacked in the schoolyard, Dale and Brennan are in a different position relative to the big tree whenever the camera angle changes.
Continuity mistake: When Nancy and Robert find the kitchen in a mess, after Brennan and Dale's sleepwalking episode, the mess on the floor and counter differs between shots. (00:22:00)
Continuity mistake: When Nancy and Robert are yelling at Brennan and Dale for fighting in the front garden the food (green beans) on the plate and the can of Pepsi in front of Dale keep on moving between shots. (00:19:50)
Continuity mistake: After Nancy and Robert ban TV for a week, Brennan throws the ice pack he was holding on the ground. The camera then cuts to Robert, and when it cuts back to Brennan again just a few seconds later, he has the ice pack again and does the exact same action as before. (00:20:40)
Continuity mistake: When Alice writes that she wants Dale to take her now, she places her wedding ring on her plate. However when she and Dale burst into the room the second time, she is wearing her wedding ring again.
Continuity mistake: In the scene where Brennan is showing Dale his sword with Randy Jackson's name on it, his hands switch from having one hand on the hilt to both hands and back when the camera angle cuts to behind Brennan, and back again.
Deliberate mistake: Director Adam McKay states on the commentary that they went to the island Catalina for location searches and realised that he did not really like the island. Instead, on the coast and during several scenes, the island of Catalina can be seen in the background. He chose not to have it digitally edited out as a joke.
Continuity mistake: In the step brother's bedroom, while Brennan is singing "Let's give 'em something to talk about" there is a Samurai sword on the floor in one shot. When they cut back to the same shot the sword is gone.
Continuity mistake: When Dale and Brennan are in the bedroom after their parents just told them that they are selling the house, Dale is sitting on the bed with the mask on. In some of shots, his legs go from being crossed to different positions and sometimes they are flat on the bed. Also, as Brennan sings and Dale is on the side of his bed, his legs change positions.
Visible crew/equipment: At the end of the singing car scene, when the range rover swerves around oncoming traffic, you can see a police officer stopping civilian traffic in the background of the shot. (00:24:25)
Continuity mistake: In the first scene of Dale and Brendan climbing on to the gilded lady when it is in the tree, when they're climbing up the ladder and shout "pirate hats!" there's a man visible in the background, but a couple of shots earlier when they walked out of the house there's an overhead shot showing no-one nearby.
Continuity mistake: When Dale and Brennan first meet at the mixer, a lady with a big blue hat keeps appearing and then disappearing in the background.
Continuity mistake: When the school bullies walk over to Dale and Brennan, the field goes from being bathed in sun to completely shaded over. (00:42:35)
Answer: It was John Woo's trademark long before a Charlie's Angels film was made.
GalahadFairlight