Revealing mistake: When we see Dark Helmets' hoverjeep in the desert, watch the front end: you can clearly make out the edge of the mirrored box they used for the "hover" effect.
Revealing mistake: In the scene where they're tumbling down the hill, Buttercup has a beard.
Visible crew/equipment: When the trio are driving to the City Deposit/Federal Reserve Bank, in the shot just before hitting the white/red booth, the extended crane arm with the second camera and seated cameraman are visible behind the booth (for filming from opposite angle). (01:03:25)
Continuity mistake: When Owen arrives at the hotel to meet Neal and Del to drive them to the train station, Owen is wearing gloves on both hands. As he introduces himself and shakes their hands, Owen's right hand is now bare even though there wasn't enough time to remove the glove. (00:33:55)
Visible crew/equipment: In the scene where Derek pulls the large knife out of the alien's foot and gets blood on his face he stands up and almost falls of the cliff. To the left in this shot you can plainly see a crewmember in a dark blue shirt, probably there to jump in if an accident should happen. (00:15:20)
Continuity mistake: After trying to entice the primitive tribe with flashy clothes and a boom box, Alvin and Simon get tied to a hut. The four ropes around their wrists are initially tied together in one knot right above their heads. But once they notice that Theodore is being pampered like a god, Alvin and Simon's wrist ropes are suddenly knotted separately instead. (00:51:05)
Visible crew/equipment: When the blob just misses Laverne, you can see a crew member under the raft (probably operating the mechanical special effect).
Revealing mistake: When Jack is hanging out of the truck you can see him standing on the hood of the car which Lydia is driving. At some points we get camera view from the back seat of the car. In some angles the mirror inside the car disappear. This is to prevent us from seeing the camera. (01:04:15)
Continuity mistake: At the end of the movie when Tackleberry glides down the balloon you can see that the color/shape of the balloon changes between the closeup and far off shots.
Other mistake: When He-Man is fighting against the centurions on the floating disks, he tells the others to get inside a building. As he opens the door to the building, not only does it fall right off the hinges, but his sword also falls right off his back, pulling his cape off with it just as the scene ends. (01:09:20)
Factual error: When they are driving back home from the holiday cottage you can clearly see an M25 sign in the background. The M25 didn't exist in the 60s.
Continuity mistake: In the scene at the beginning of the movie where the flying vampires are chasing the security guard across the boardwalk parking lot, the positions of his arms as he is running changes back and forth between shots. In the close-ups of the guard's face, his hands are up, holding his hat down on his head. In the wide shots, his arms are down at his side. (00:02:45)
Visible crew/equipment: Loretta calls for Ronny at the bakery, and when he picks up the phone then promptly hangs up on her, the dark protruding outline of the microphone wire is visible at his right side. It happens again when Loretta visits the bakery and Ronny tells her Johnny took his life from him. Additionally, later when Ronny and Loretta spot each other at the fountain in the Lincoln Center Plaza, there appears to be an actor's mark at Ronny's feet. (00:25:00 - 00:27:05)
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)