Continuity mistake: When Brennan rubs his nuts on Dale's drums, Dale comes in and starts fighting with him. Brennan doesn't have a chance to put "them" away but in the next shot his zipper is up.
Continuity mistake: When Dale tells Brennan he needs to hear him sing, Brennan has a sword and is swinging it around. After he sings, he gets up and the sword is shown on the floor in its scabbard. They flash to Brennan, then back to Dale and the sword is gone.
Suggested correction: He places it down before sitting on the bed to sing.
Factual error: A video is shown of Derek Huff singing "Ice Ice Baby" at a school talent show that took place when his brother Brennan was 17. Robert states his desire to retire in "in two years," in 2010, making the movie's setting 2008. 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 the summer of 1990.
Character mistake: When Brennan's brother is talking to Jack in the kitchen, he is holding a Heineken beer. However when he goes out in the tree house and shows the brothers his six pack, he claims he hasn't had a carb since 2000.
Continuity mistake: The bottle of ketchup in the dinner table scene, early in the movie, alternates from right side up to upside down, from shot to shot. (00:08:45)
Revealing mistake: 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 mistake: In the scene where Alice spells words with her food on her dinner plate asking to have sex, the very next view of her shows a smaller plate in front of her.
Continuity mistake: 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. (00:07:00)
Revealing mistake: In the dog poo scene, as Brennan is licking the poo, you can see it's a powdered donut.
Continuity mistake: 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. (00:57:45)
Continuity mistake: In the scene of the step brothers' first dinner together, Will Ferrell can be seen picking up a French fry, but in the next shot he is holding a half eaten chicken nugget. (00:08:30)
Continuity mistake: When Dale and Brennan are fighting over the drum kit, Brennan throws Dale into the gong and it falls over. In the next shot it is standing again. (00:18:15)
Continuity mistake: 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. (00:10:15)
Continuity mistake: At the Catalina Wine Mixer, Brennan Huff's voice breaks the large glass/ice helicopter sculpture. A few moments later, his step father is clapping and the helicopter sculpture is visible behind him. (01:22:45)
Continuity mistake: When Brennan and Dale are in the tree house and Brennan's brother comes up, Brennan has a magazine in his hand, and each time the shot changes, he doesn't. It alternates between the two. (00:27:55)
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: When Brennan and Dale are talking about the drum set in the living room, you can see a crew member on the glass window.
Continuity mistake: Near the start when Nancy and Robert first meet and are undressing themselves, 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. (00:02:10)
Visible crew/equipment: When we see Nancy, Robert, Dale and Brennan on the boat, as the camera pans past Robert and Nancy, you can see the camera reflected in the shiny post of the boats wheel. (00:14:55)
Continuity mistake: 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. (00:27:15)
