Revealing mistake: A quick mistake happens when Brenda and the girl crawling out of the TV get in a fight. Brenda throws the punch, the other girl falls over, and for a quick second her dress flies up too far and you can see where the makeup (that makes her look dead) on her legs end and you can see her real thigh.
Continuity mistake: When the two girls are hitting each other with random objects, you can see Pamela's underwear just above her skirt line, but in the next shot it is gone.
Continuity mistake: When Tom rips off the Michael Jackson nose and we see a close up shot of it, it has all jagged edges. But in the next shot when Tom picks up the rest of the costume outside, it is a perfect circle where the nose used to be.
Continuity mistake: After George has closed the well, the alien appears. Cody and Cindy gasp, and you see Cindy putting her arm on Cody's right shoulder. George climbs up from the hole and puts his hand on Cindy's shoulder. When it cuts, Cindy's hand is on Cody's left shoulder and George's hand is on Cody's right shoulder.
Continuity mistake: In the scene with Brenda's wake, notice how Brenda's eyes change. In one shot they are wide open, in the next they are closed. This changes several times during the scene.
Revealing mistake: When Cindy hits Cody with the end of the sledgehammer, you can see that the hammer hits the clothes behind Cindy rather than Cody.
Revealing mistake: When Tom comes down to the basement you see him coming down a narrow stairway. Later when Cindy says "there's something on the other side of the door", you can see a shadow walking back and forth behind the door. That shouldn't be possible unless the thing behind the door can walk through the walls in the narrow stairway.
Continuity mistake: When Cindy is surfing the Internet for the lighthouse, you see her clicking on different links. When she has clicked the "Page4" link, you see the mouse pointer start moving. Then it cuts to Cindy and back to the screen again. You can see the mouse pointer move from the exact same position in the exact same direction.
Continuity mistake: When Father Muldoon is knocking on Cindy's door, she walks towards it. It is a frosted glass door, but you should be able to see if someone is standing behind it. We can't see Muldoon standing there at all. It cuts to Cindy opening the door, and then back to Muldoon standing in the door opening. We can also see a painting in the hall, and when Cindy closes the door we can see the painting through the glass door. How come we didn't see Muldoon?
Continuity mistake: When Tom is talking to George at the farm about his hip-hop dreams, on his right hand he is wearing a glove and is also holding another glove. The glove stays on all during the conversation, and we never see him take it off. Then, when George gets his head stuck in the bus, you can clearly see both of Tom's hands - empty.
Continuity mistake: When Brenda is fighting the girl that comes out of the TV, her hair changes between shots.
Other mistake: When we first get to see Tom's house it is that there is nothing else than a corn field on the left side of the entrance to the house. Later when we see Tom running out of the house looking for Sue, trees and bushes suddenly appears on the left side instead of the corn field. Also the above shot of the house property later doesn't match what we've seen earlier.
Continuity mistake: When father Muldoon has arrived and asked where Cody is, there is a shot of the table where Cody just sat and you can also see a shelf on the wall. Later, when Cindy comes back home and finds George lying unconscious over the table the shelf is different and is screwed on higher up the wall.