Other mistake: When we see the "regulators" riding over the hill on the way to kill Django and Schultz, if you look carefully at the right-center portion of screen, you can see one of the stuntmen fall off his horse and the horse continues to run down the hill without him. To make matters even worse, it appears the stuntman rolls right in front of another horse and gets trampled. (00:41:00)Spencer Crouse
Factual error: While Bridger is watching the film of the Mafia boss following Beckerman he signals for the film to be stopped so he can look at the close up shot of the man. He is watching a 16mm film shown through a bog standard projector - stop a film like that for more than two seconds without closing down the projector shutter (this doesn't happen - if it did the screen would darken instantly) and it will melt and catch fire. This doesn't happen.
Continuity mistake: Gimli is lying with his face under the water, after jumping off the Deeping Wall and landing on the Uruk-hai. In the close-up, the right arm that grabs Gimli's shoulder to help him out of the water is Legolas' right arm. Yet, in the wide shot, suddenly it is Aragorn helping Gimli to his feet, not Legolas. (01:11:10)Super Grover
Continuity mistake: The tyres on the crotch rocket motorcycles they were riding kept changing from knobbly tyres to road slicks, back and forth depending on what terrain they were on. Easiest to see when Ethan skids on the road to avoid the white van - clear shot of slick tyres - then about 30 seconds later they're on the dirt, he skids into the old car and you can easily see that he's got off-road tyres front and back.
Visible crew/equipment: When Pee Wee is chaining up his beloved bike you can see the long chain coming up through the bottom of the bike box. Full screen version only. (00:13:40)
Plot hole: Isn't it rather strange that nobody outside the Howard family's small town expresses any interest in the confirmed discovery of a new human sub-species, the only one on the planet? Wouldn't it be more likely that their little backwater town would be inundated with every press and scientific organisation on earth, and that the Howard family would be the centre of the greatest publicity carnival of all time?
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.
Factual error: While handling the ignition coil cable to the distributor cap, Joe Pesci tells De Niro that the timing chain needs adjustment in his truck. A truck of that year with an inline Chevy motor would not have a timing chain at all, instead this truck would be equipped with a direct drive timing gear. Even if it had a timing chain, it would be behind the water pump and a cover. It would have been a several hour job to replace, not possible to adjust it.
Continuity mistake: When they are looking at the house and they get out of the car, the one man on the passenger side leaves his door open. When they walk to the side of the house and come back to the front, you can see the car in the background and the door is shut.
Continuity mistake: After Mark is found, he runs into Kate's arms and hugs her and her sunglasses fall off her head, but then in the very next shot they're back on her head perfectly. (01:24:50)
Other mistake: When Adam comes in and says "when I woke up this morning, the pain was gone", Connie is mouthing his lines behind him.
Continuity mistake: If you look carefully at the monster (Frankenstein) you will see that his face is different in the ending scenes. The reason is, during the movie you see the monster take the woman doctor and throw her out the laboratory window. You then see the monster kind of stumble, which he really did and broke his ankle. So in the final scenes they replaced Lon Chaney Jr. as wolfman with a stuntman, and Lon Chaney Jr. finished the movie as the monster.