Revealing mistake: When the Angels are fighting the "Creepy Thin Man," right before Drew Barrymore lifts up Lucy Liu to spin her around and kick the thin man, to get Lucy's attention, Drew hollers out "Lucy!" even though Lucy Liu's character's name is "Alex." (00:26:20 - 00:27:25)
Revealing mistake: When Carl is being dragged away by the demons, you can see the cable line that he's attached to. May be fixed on DVD.
Revealing mistake: In one shot when the boat is pulling away from the waterfall, you can clearly see that the shot is the same one they used earlier in the movie. The water from the waterfall now is going up the cliff! They have just put it in reverse.
Revealing mistake: When Dracula flies into the room to stop his brides from devouring Jonathan, the board carrying him is visible. (00:34:10)
Revealing mistake: When Louis gives Gage the lethal injection, because the syringe is transparent you can actually see the prop needle retract in and out of the syringe as he supposedly injects Gage.
Revealing mistake: There are supposed to be two dead young Asian males sitting in the back of the car, but in this shot, it is so obvious that there are two dead 'dummies' riding in the back. Also, in the crash, a few seconds later, very blatant dummy heads are flying everywhere. (00:40:40)
Revealing mistake: When Luke is being fed to the Rancor, in Jabba the Hutt's dungeon, there are black outlines around the beast's legs, from the composite's blue screen special effect. This was edited out in the special edition rerelease.
Suggested correction: This was not a "mistake". The outlines showing around the beast's leg were due to the limited CGI technology at the time the film was made. With advances in special effects in the following decades, the filmmakers were able to enhance the CGI quality in later releases.
But it is a mistake to show that the Rancor is not real, and the outlines show that. It's certainly not intentional.
Not sure what you mean that the rancor is not real. Of course it's not real. The issue is, at that time, it was not technically possible to show the beastie without the lines showing. I classify a mistake as something that was not intentional. In this case, it was, due to the limitations of CGI in the 1980s.
Revealing mistake: In some extended edition cuts of the film, Regan backwards spider walks down a flight of stairs, and blood falls from her mouth. But her face isn't that of Linda Blair, but of a stunt double.
Revealing mistake: In the scene when the main character is in the library on the internet, she goes to a couple of websites. When the shot shows the URL up top, it is C:\windows98\mydocuments\etc.html. Instead of actually searching on the web they used a premade html page and accessed it from their computer.
Revealing mistake: When Peter Parker first discovers he can climb up walls (while in citizen clothing), he tests it out by climbing up a building in an alley. During this scene, you can clearly see his clothes hanging out forwards, indicating that the scene was filmed with him crawling along a floor horizontally. (00:24:50)
Revealing mistake: In the scene where the Terminator and the T-1000 are fighting in the corridors of The Galleria, the Terminator has fired multiple shots at the T-1000. When he gets up off the floor, the Terminator throws him into the left wall and the impact hole is already visible before he hits. (00:31:45)
Revealing mistake: In the freeway chase scene when one of the agents jumps onto the hood of the first car then jumps off, the car flips, then a second later as the car is still flipping you can see the gas tank and transmission have been removed. (01:23:45)
Revealing mistake: After the woman is strangled and the people come in trying to find the little kid, the dead woman is clearly seen blinking. (00:11:25)
Revealing mistake: When Leo is laying his dead kids on the grass, the little girl keeps moving her eyes and breathing.
Revealing mistake: When Ace and Melissa are in bed together having sex if you look close enough you can see that she is wearing underwear. (00:45:35)
Revealing mistake: After the helicopter escape at the end, a red sports car is sticking nose-down in the ground after falling hundreds of feet down out of the aeroplane, without a single crack in the windscreen, in mint condition. The yellow one only has the right door open. (01:59:30)
Revealing mistake: Right after Nell sends Hugh to hell, Dr. Marrow and Theo come out of hiding behind a pillar. As Marrow puts his hand on the pillar, it squishes in as if it was made of foam rubber, instead of stone. (01:39:50)
Revealing mistake: The kid in the wheelchair is playing a Game Gear with no game in it.
Revealing mistake: When the new Pope is announced, the New York Times headline is shown, and 'Copyright 1990 The New York Times' is visible. The event took place in 1979.
Revealing mistake: When the kids are burying Gus, his supposedly dead face flinches when they shovel dirt on him.