Factual error: In the very first scene in the film when the magazine covers are flashing up, the very first one has a headline which says "loose that belly". For a film whose title has the word "lose" in it, you'd think that they could spell this properly.
Continuity mistake: When Andie brings the dog into Ben's office, Ben, Thayer and Tony are standing around listening to Ben complain about how Andie is driving him crazy. Tony is holding a white mug with black writing on it, and he hands Ben a plain black mug. Just as Andie walks in, the shot changes to her, then back to Ben and his friends. However, now Ben has a gray colored mug and Tony has a black one. (00:50:15)
Continuity mistake: NBA Finals-Game 1. Andie wants Ben to buy her a Coke. During this scene, the camera cuts back and forth between Andie and Ben, and the basketball game. When Ben first looks at the game clock there is a little over a minute left in the game. He rushes to get her soda, and when he gets back, she says she wanted Diet Coke. There is a shot in this sequence where the camera is filming the basketball action, and you can see the game clock with over 7 minutes remaining, even though they are supposed to be nearing the 30 second mark. (00:33:35)