Continuity mistake: When Harrison Ford is on the rooftop and the suitcase accidentally opens, the Statue of Liberty goes flying off the rooftop and on to the ground, several stories down. In the next shot, the little statue is perched at the edge of the rooftop. Also, the clothes that fly away magically reappear next to the suitcase a shot later.
Revealing mistake: Near the end of the film, a B-52 seen flying across the screen. The bracket holding up the model is visible.
Continuity mistake: Anderson (Gene Hackman) visits Clinton Pell's wife and she's talking about Genesis 9, verse 27. In the first shot he's standing right behind her. In the next shot he stands on her left side. Then again right behind her.
Continuity mistake: About 40 minutes from the end (I think - Michelle Pfeiffer is on a beach with Dean Stockwell), a boom mike comes in from the bottom of the screen very obviously, taking up about a third of the screen.
Continuity mistake: At the end when Michael Jackson is singing come together, at the end of the song his shirt is undone, but when the camera shoots back on him his shirt isn't ripped.
Continuity mistake: When Frank sees what he thinks is the Ghost of Christmas Future in the elevator, he flips out and accidentally clocks Grace in the jaw. She puts her right hand to her face, but in the next shot she's holding her left hand up.
Factual error: In the movie Dian touches hands with the silverback Digit. In reality Digit was a young male and not a silverback. The gorilla she touched hands with was not Digit but one called Peanuts.
Continuity mistake: When Kaneda shoots Tetsuo with his laser gun, it makes a hole on his shirt. In the next scenes, the hole is gone.
Continuity mistake: The strings of lights for the reindeer reins change continuously from one strand to two.
Revealing mistake: As Reg fights with one of the baddies with the chainsaws, as the baddie take a swing with the chainsaw he misses and cuts into the wooden door. You can clearly see that a vertical cut has already been made in the wood though, to help the chainsaw get in and cut. (01:17:55)
Audio problem: In one scene where Jackson is caught by some bad guys you can see (and hear) that a couple of times when Jackson laughs it is badly dubbed over.
Visible crew/equipment: When Joey smashes the garage door open by reversing the car into it, you can see fluorescent lighting reflected in the car windows. The garage does not have fluorescent lighting fitted inside it.
Other mistake: As the brown truck drives away in the scene after the man working in the newspaper office is "harpooned" by a Critter, if you look closely as the truck turns a corner you can see some Critters rolling after it. Well, after they roll past the truck in the bottom left of the screen you can see the Critters roll right smack into another parked car. Obviously the crew forgot to add a turning feature to their Critter balls (which were just some fur taped to a basket ball).
Factual error: Buster Franklin's bass player is playing a MusicMan StingRay bass, even though they didn't appear on the market until 1976. The guitar isn't from the fifties either, but I can't make out what it is. (02:12:30 - 02:14:50)
Factual error: At the end, when Cyndi Lauper touches the glowing pyramid, goes into a trance, and starts translating the inscription, Jeff Goldblum pulls her off and she doesn't finish it. One of the bad guys says that what Cyndi already said will be enough to help him decode the rest and that it's just a matter of "cartography" now. He should have said "cryptography" (skill of decoding secret writings) and not "cartography" (which has to do with making maps).
Visible crew/equipment: As Tina swerves off of the road after seeing her mum get killed by Jason in the middle of the road, if you look in the back of the car, you can see a camera set up, filming the shots in the back seat. (00:43:15)
Visible crew/equipment: As Zeebo is kissing Tanya, the device used to make his ears wiggle is briefly visible.
Visible crew/equipment: When Carol-Anne is running away from Kane's voice in the garage, she ends up standing in a puddle, only to have hands pull her in seconds later. But when the camera moves down Carol-Anne's body to the puddle, you can see the platform the actress is standing on.
Continuity mistake: When Celeste explains to the Elders why Earth should be saved she says, "They have sneezes", but doesn't explain what they are. The Elders don't look like they recognize the term. Later, one of the Elders sneezes, and says, "We don't have sneezes here." Now how could he know that he just sneezed, if nobody explained it to him?
Character mistake: Watson says that there are fifteen windows on the front of 221B Baker Street, but if you look, there are only twelve.