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.
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: 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.
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.
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: After the spittoon cup gets spilled on Samir's shirt, the stain changes and becomes smaller in a later shot.
Continuity mistake: When Billy and Bolger are driving down the road after the funeral, they are on a 2-lane road, with nothing but grass and trees on either side. But when the shot changes so they're facing the camera, it's a 4-lane road with a lot more traffic. Then the road becomes much bigger with a median.
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.
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 Frida is in her room and throws the stuffed animal near the window, she sees a zombie in the pouring rain across the street. However when her boyfriend startles her in the window, he is dry and the rain and wind instantly stopped.
Character mistake: Near the end of the movie Godfrey says "I'll try to send the birds to the sea," but when he redirects the birds the operator says the birds are going back to the base.
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.
Revealing mistake: When the girl is giving the guy a blow job in the school restroom, he finishes in her mouth. She goes to the sink and spits it out. You can obviously tell she had a mouthful of water going by the color and quantity. (00:20:45)