Continuity: After arriving to the new house, Brennen is seen in the car as Nancy and Robert talk to the neighbor (Don). Brennen's Arm is seen up holding the handle on the interior of the car near the window then down between each shot.

Revealing: Brennan buries his brother, Dale. When Dale emerges from the ground you can see a blue material burst out as he emerges.

Continuity: 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.

Continuity: When Brennan and Dale first meet and they are standing on the front lawn and they tell each other that they have to be called a certain nickname, when the camera is zoomed back, it shows them really far apart from each other. But when it shows from Brennan's or Dale's point of view, they are closer together.

Factual error: A video is shown of Derek Huff (played by Adam Scott) singing "Ice Ice Baby" at a school talent show that took place when his brother Brennan (played by Will Ferrell) was 17. Brennan is 39 in the film, placing the talent show 22 years ago in 1986. The song "Ice Ice Baby", recorded by Vanilla Ice, came out in summer of 1990.

Continuity: After the first dinner scene with the family, Dale finally decides to leave and head upstairs. He places his napkin down next to his plate. In the next shot it has vanished. It then reappears a few shots later.

Continuity: 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.

Factual error: In the film, the Catalina wine festival supposedly takes place on Catalina Island. Yet in a couple of shots you actually see Catalina Island in the background. That's because they are actually at Trump golf course in Rancho Palos Verdes and the island is 26 miles across the sea.

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.

Continuity: 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: 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.

Continuity: In the christmas scene where they are decorating the tree, we see Robert eating a christmas-tree shaped biscuit. When he gets up, the biscuit is suddenly larger and more whole than before, where it was almost finished.

Revealing: In the scenes in which Brennan and Dale are fighting with the young children in the park, it is clear that in quite a few shots the children have been replaced with doubles.

Continuity: When Brennan and Dale first meet on the front lawn, they stand and stare at each other for a while. With every shot change, it continues to change from either being sunny or shadowy in the spot where Brennan stands.

Continuity: When Brennan and Dale are in the tree house and Derek comes up to talk to them, the soda can over Derek's shoulder moves around between shots.

Continuity: 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: Near the start when Nancy and Robert first meet and are undressing themselves in a hectic lust for one another, Robert removes his jacket in a wideshot and his shirt and tie are still on. But in the next closeup the tie has vanished and he is suddenly unbuttoning his shirt.

Continuity: When Nancy and Robert are yelling at Brennan and Dale for fighting in the front garden (and ban television for a week) the food (green beans) on the plate in front of Dale keeps on moving between shots.

Continuity: 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.

Continuity: In the scene of the step brothers' first dinner together, Will Farell can be seen picking up a French fry, but in the next shot he is holding a half eaten chicken nugget.