Continuity mistake: As Hank tells Bill & Dale that they are going to drain the quarry (whilst in Dale's basement) and Dale lets his burning cigarette drop. Dale & Bill start to freak out and it goes to a wide shot of the three of them & the cigarette Dale dropped is not on the ground anymore.
Continuity mistake: When Hank, Dale & Bill go to the quarry to get the car, they use a tow truck to try and pull it up. If you look at the tow truck you can see it is a red color. Later on when the protesters come and are sitting in a circle and singing the tow truck is now orange. It stays orange for the rest of the scene.