Continuity mistake: When Kutcher and Peet are in the restaurant, the amount of water in their glasses change from full to empty to full to half full, in about one or two scenes.
Continuity mistake: When Ashton Kutcher and Amanda Peet are in the restaurant, they spit water at one another repeatedly and Ashton's shirt becomes quite wet. In the next shot, his shirt is almost completely dry.
Continuity mistake: Near the beginning of the movie a liquid is thrown at the windshield of a car, completely obliterating the view through it. In the next shot, before another liquid is being thrown at it, the windshield can be easily seen through with only slight evidence of the previous liquid.