Revealing: After the bounty hunter, who changes three times throughout the movie, changes into the Reverend, he is in front of someone else who is a stand-in for the real Reverend but is obviously not.

Visible crew/equipment: At the end when Harv leaves, you can see a crew member reflected in his car window. It's not any of the Brown family members, because they are walking to their house.

Audio problem: When Brad puts his plate on the floor, the cat comes out from under the bed. You can hear it meow, but it's mouth doesn't move.

Continuity: After Charlie shoots April in the ass with the slingshot, she immediately turns around to see who did it. Charlie is holding it as he says "Oops" and Brad takes it from him, all the while April is turned completely towards them. Couldn't she see it was Charlie and not Brad?

Deliberate "mistake": The explosion of the ship at the end of the film is actually another angle of the explosion of the house from a few seconds earlier. The craft's explosion is much too small for what is shown in the film.