Continuity mistake: After Todd Howard knocks out his opponent in the boxing match, the crowd immediately starts throwing cups of popcorn into the ring. The camera cuts to Todd cheering and then an overview shot of his opponent laying face down on the canvas. At that view you can see that there is no rubbish or popcorn or anything else in the ring. Then when the camera cuts back to a side view there is loads of rubbish and popcorn all over the place once again.
Other mistake: Near the end of the movie, in the mansion overlooking the water, James Woods is eliminating the bodyguards. As he shoots the one at the bathroom sink, blood sprays all over the mirror, but the bullet never breaks the glass.
Continuity mistake: Near the beginning of the film, the soldiers are filling sand bags with mud. Beletsky, whose hands and forearms are covered in wet mud, puts down his sandbag and takes out a photo of his girlfriend. In the next closeup shot of him holding the photo, his hands are suddenly clean and dry. (00:11:00)
Continuity mistake: When the angel lands face down in the pool, Michael Knight turns her over and her face is completely dry.
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.
Audio problem: At the beginning, when mother and daughter arrive from New York, they try to find someone who can take them to the Sullivans'; while working this out, there is a man playing a guitar; in the beginning, everything's fine, but soon his hand movements don't match the sound.
Continuity mistake: During the dinner quickly interrupted by the record. Anthony Marston raises his glass to Vera, but his hand was nowhere near the glass in the previous shot - not even on the table. (00:14:30)
Factual error: In the farmhouse bedroom scene, the lead character wakes up and a close up shot of the alarm clock shows it is 5AM. Full sunlight is coming through the window, and an exterior shot shows the sun shining on the house and hay bales. The narrative lead-in just explained that it is early October on a farm near Dallas, Texas. The earliest sunrise occurs near Dallas in October is 6:40AM. (00:04:00)
Continuity mistake: When Jamie gets out of her car, her leg warmers reach down to her heels. In the next shot, they've been pulled up to just her ankles. (00:07:05)
Continuity mistake: In their first meeting, Rick Latimer stubbornly holds his hand out to Jake Phillips until he properly shakes it. Louis Gossett Jr. takes his baseball cap off in close-up, but in the reverse shot he still has it on his head. (00:14:50)
Character mistake: When Modoc is suggesting what type of blood to drink, he suggests pigs blood B-. Swine don't have B blood. They have A and O blood only.
Continuity mistake: When Molly Ringwald is on the phone at the club and gets approached by the girl in orange, throughout the whole conversation the position of the phone receiver in Randy's hand is wildly inconsistent. (00:09:30 - 00:11:00)
Continuity mistake: When George's wife asks him what made him drive all the way out here, their car is on the back of a large dinosaur at that moment. When it cuts to a closer angle for his reply, suddenly they are on a dirt road.
Revealing mistake: When the skater (a dummy as a matter of fact) is blown away no blood or guts spill around.
Revealing mistake: There are times in the movie when you can tell Bobo's beard is fake such as when Penny's giving him a drink from a 7-11 and it's peeling off near his right ear.
Plot hole: The fact that Buddy placed the knife and note in the steering wheel of Jerry's car is unrealistic. Buddy first met Jerry in the bathroom after school started and Jerry hasn't gone outside of the school building to his car until this point later in the morning... so there's no way that Buddy could have known which car was Jerry's to pull this stunt.
Revealing mistake: When Frank Bauggs is falling from the building, he is a very obvious dummy. His body limps around too much. (00:50:45)
Revealing mistake: Terri is replaced by a stuntman in a dark blond wig once she puts on her motorcycle helmet outside the hardware store.
Revealing mistake: A bunch of seedy individuals are gathered, weapons in hand. Unbeknownst to them, though, deadly ninjas are creeping by, with all the speed of fast-forwarded footage. The problem, besides how obvious the trick is, is that it also features a visible jump cut; you can see the foliage change position literally from one frame to the other during the same shot. (00:01:30)