Factual error: Near the beginning of the film there is a map of Europe with the countries coloured in using their respective flags. Great Britain is coloured with the Union Jack (Union Flag) pattern but so is Southern Ireland (Eire). Southern Ireland is not part Great Britain, only the British Isles - they are a separate country and the Union jack is not their country's flag. Only the north or the Irish landmass (Northern Ireland) and Britain should show the Union Jack. If they are using an "old map" it would have to be very old, before the 1920's.
Continuity mistake: In the scene where the gang is at the Vatican and Jenny tells the guard that Cooper is retarded you see cooper bite into the ice cream cone and it falls apart. However when you see Cooper a few seconds later and the guard talks to him the ice cream cone is back to its original shape.
Continuity mistake: When Cooper wears the burning hat, the fire is burning roughly the top third of the hat, yet, in the following shots where he tosses it back and forth with Scott, then throws it in the fireplace, only the tip is burning and everything underneath the small flame is undamaged.
Continuity mistake: In the graduation party scene, when the band starts singing "Scotty Doesn't Know": Just as the main chorus kicks in, Kristin Kreuk starts dancing on stage. The film cuts from a close up to a wide shot of the stage and Kristin is waving her red jacket around and throws it in the crowd. The shot then goes to close up and mysteriously the jacket is back on her again. It's short and you can only see parts of her shoulders, but they are red.
Continuity mistake: When Jenny, Jamie, Cooper, and Scott are walking down the Amsterdam highway, they switch places from shot to shot. First shot we see is of their feet and you can see Jenny is on the left hand side in front, and Jamie is on the right hand side in back. The shot cuts and now Jamie is in front, left hand side, and Jenny is on the right hand side in front. When the shot changes again they switch shots.
Continuity mistake: When Cooper is at the sex club and the dominatrix Madame Vandersexxx hands him the paper with the safe word on it, he takes it and goes to put it in his shirt pocket. The scene cuts and he is holding it in front of him again, then in a few seconds puts it in his shirt pocket.
Continuity mistake: In the scene where the gang first meet with the weird Italian guy in the train and he puts his hand on Jamie's leg, look at Jenny. She is sitting right next to Scotty but when Cooper and Jamie run to the opposite side of the coupe she is sitting about a metre away from Scotty.