Factual error: At the end when the shark is attacking the boat and the electronic device is used you can hear the shark roar. Sharks cannot produce this sound since they have no vocal cords.
Other mistake: Max says that Michael is the "Man of the house" and won't come in until he's invited, which Michael sarcastically does, except Michael isn't the man of the house - its actually his grandfather who owns it.
Visible crew/equipment: When Ashley is running down the corridors before escaping back into her medical room, you can see the dolly that The Engineer chasing her is being pushed on. (01:04:50)
Revealing mistake: As the Predator tends to his wounded leg, one of his claws can be seen bending as if made of rubber.
Visible crew/equipment: When Ash crashes his car into the tree stump and is ejected through the windshield, you can see the wire attached to the dummy pulled through the windshield. (00:12:35)
Visible crew/equipment: When Annie Lansing is looking out of the back of her car to see if the hitchhiker is still running behind her, he has disappeared but instead you can see a crewmember through the upper left corner of the car window.
Continuity mistake: During the opening credits, Kristen is making a Papier-mâché house, and in the process, her hands become covered in mixture. However suddenly both her hands are completely clean. (00:02:10)
Continuity mistake: When Daryl first meets Sukie, he has 4 scratch marks on his face, but when they play tennis, he only has 1, and then in the swimming pool, it's back to 4.
Continuity mistake: When the two cops pull the stripper over, their car stops in the middle of the road. When Beck and Gallagher pass them later, however, their car is closer to the pavement. Their car moves yet again when Beck looks back at them out of his window. Also notice that three headlights are now on, including one that the stripper blew out. (00:51:30)
Visible crew/equipment: When the zombified Tony chases Susie through the supposedly empty health club, crew members are seen standing at the left side of the screen.
Revealing mistake: Just before Walter throws Lisa through the window, you can tell that Lisa is a stuntman wearing a wig.
Audio problem: In the mansion, the boys open a secret passage and fall through the floor. They scream after shining a flashlight on a skeleton. Eugene then can be heard whining that he wants to go home, but his mouth is not moving.
Continuity mistake: As Jesse, Diamondback and Homer try to black out the windows on their car (to protect themselves from the sunlight) Homer spray paints the window next to him black. The camera angle switches to a wide shot as the car drives by. At this time, the back window (which was just blacked out) has not been spray painted yet. It is totally clean again.
Continuity mistake: When Jerry throws all the knifes on the table he picks up a certain knife. It cuts to another shot and you see him pick up the knife again, but it isn't the same knife anymore. The knife he picked up in the first place is still on the table. (01:12:25)
Visible crew/equipment: When Jesse is in the kitchen trying to get the skull from the bird's mouth, you can briefly see the puppeteer operating the bird in the lower right corner of the screen.
Visible crew/equipment: The boom mic is visible when Sally sings her "Pie in the Sky" song and when Courtney and Sally are standing in the bathroom, before Sally's face explodes.
Revealing mistake: Toward the end, after Ricky decapitates the old Mother Superior, a young nun assumes she is alive and taps her shoulder. Mother Superior's head falls off and to the floor. There is no blood whatsoever. The old woman had just been decapitated moments earlier, and there isn't even a drop of blood, not even on the white part of her nun outfit at the neck.
Visible crew/equipment: In the scene near the end of the movie when Judy's father is smashing up the doll maker's work and fighting with Mr. Punch, a crew members hand is very visible working Mr. Punch.
Continuity mistake: When he puts the pins in her eyes, evey time it is shown it's different - sometimes they are all covered in blood, sometimes only some of them or one, and sometimes there's no blood at all.
Other mistake: Despite the noise of the demon in the house, the tornado clouds outside, the flashing lights from the demon exploding and the fireworks in the sky - not a single neighbor is anywhere to be seen. Even after daylight breaks the neighborhood is a ghost town as we pan away from the actors.