Continuity mistake: After Nick becomes a hero, he wears a cast on his right arm. However, when he and Kate go to dinner with Kate's boss, Nick's cast mysteriously disappears for one shot. They are sitting at the table at the beginning of the dinner and Nick picks up a glass with his right hand, with no cast. The next time you see Nick, he has a cast on his right arm again.
Continuity mistake: There is a scene where Kate comes home and her mother is standing right there. Kate starts yelling at her mom. When Kate first comes in the door she puts her purse behind her back on the counter and the purse is leaning on her back. If Kate were to move, the purse would have fallen on the floor. In the next shot, Kate is further away from the counter and the purse is standing straight up as if it was put there like that.
Continuity mistake: Towards the end of the film Kate is confessing her secret to her boss. We see a close up shot of Sam closing his folder, then sitting forward in his chair. When we see a long shot of the room Sam is clearly sitting back in his chair with his folder resting on his knees. But when we see a close up shot of him again he is sitting forward with his elbows resting on his knees.
Continuity mistake: When Aniston goes to meet Nick at a cafe, after he has become famous, the waitress brings her a drink. Throughout her discussion with Nick, she doesn't take one sip, however, as Nick gets up to leave, Aniston's glass only has about an inch of liquid left in it, even though she didn't drink the whole time!