Continuity mistake: After the spittoon cup gets spilled on Samir's shirt, the stain changes and becomes smaller in a later shot.
Continuity mistake: During the scene when Ian is taped to the chair, the duct tape across his shoulders changes from shot to shot. Some times it touches the shoulder seams on his shirt, and other times it is several inches away.
Factual error: At 01:29:08 we see Carys lying despondent on the couch in her living room surrounded by balled up tissues, empty food containers/soda cans and trash - all the signs of going through a bad break up. She gets up to answer the door for her mom, who has brought by a plate of cookies. Carys sits on the couch again, looks down, looks up, and by 1:29:40 the entire room is clean; we see her mom fluffing a pillow. There is no way her mom could have cleaned the living room in less than 32 seconds.
Factual error: About 30 minutes from the end, the rodeo parking lot is shown, with the cars parked 3 deep (i.e., 3 cars parked nose-to-tail). Valet parking? At a Wyoming rodeo?
Factual error: When the Lincoln Continental Convertible was rolling backwards down the hill, Nick put his hands on the trunk to try to stop it. A car, especially one weighing 5,000 - 6,000 #, would easily knock over a person and possibly cause serious bodily injury (even death). Nick's attempt to stop the car by holding onto the driver's door handle would also be futile and potentially dangerous. (00:37:47)
Plot hole: Mr. Cranston asks Denise to be the accompanist for the school's production of "Chicago". This is an error. In the year 2009, in which the film is set, this would be impossible since the licensing company which has the theatrical rights for "Chicago" restricts the show from being produced (even by amateur groups and schools) anywhere in the greater New York area while there is an open-ended production running on Broadway.
Other mistake: During the shot where Katy holds her cellphone up to her computer screen, it is seen that Andy's video has 27,000 views. A few shots later, though, Andy claims it has half a million views and is the top featured video on the site. (01:05:25)
Continuity mistake: When Joel and Dean sit at the booth to talk, Dean places two beers on the table such that the labels are facing the camera. As they talk and the camera switches back and forth between the two friends, Dean's beer switches orientation showing the label in some shots and not in others, despite the fact that he does not touch the bottle whatsoever. There isn't enough time between shots to allow him to move the bottle or drink any as the bottle remains full.
Continuity mistake: In a "movie inside the movie" moment, Arshad Warsi is on the witness stand. In the wide shot the hand he had on the book is held up gesticulating, and at the end of the shot he has his hat in both hands, while it is under his armpit in the shots from the front. (00:12:55)
Continuity mistake: When the main characters visit Montreal and with their friends they go out to eat at a diner and he creates a "home" out of 4 toothpicks, 3 sugar cubes and a coaster. As the camera goes back and forth in the conversation, watch the "home" on his plate of pancakes. It falls and appears to be scraped and turned in a different direction on his plate by the end of the conversation.
Continuity mistake: During the sex scene between Alex Pettyfer and April Pearson, April Pearson is not wearing a shirt. However, as Alex Pettyfer is dragged out of the car, she is suddenly wearing her shirt again.
Other mistake: When Lisa and Toby are out, they are drinking Beck's Blue, a non-alcoholic version of Beck's, yet they still appear to be drunk. (00:39:30)
Continuity mistake: When Lotte is tied down to the altar and is talking to Jimmy, the cut on her face alters constantly from the left cheek and right cheek throughout the conversation.