Revealing mistake: When Barry is arguing on the phone with the Healthy Choices employee, the map on the wall behind him is creased in the Texas/Arkansas area before he punches it there. This could perhaps be the result of a previous take or some sort of indication of where the soft spot in the wall is so that Adam Sandler doesn't really break his hand.
Continuity mistake: The scene where Barry and Lena meet at the hotel is shot very artistically. We only see their silhouettes when they fall into each other's arms, and immediately after that the silhouettes of an endless row of people rushing by them in both directions. However, in the shots before we saw each of them running towards the other, and there was absolutely nobody around except them. In addition, some of these other people walk by more than once, like a tall slender lady with flying hair.
Continuity mistake: When Sandler is demonstrating the new line of 'unbreakable' glass toilet plungers he smacks one on the table, it of course shatters and pretty much all of the white stuff inside comes flying. Yet later we see Sandler carrying the broken plunger handle with a lot of the contents still inside.