Revealing mistake: After Mary Robert jumps out of the car, you can see the stunt double falling for her.
Revealing mistake: When the scientists inject the mouse with poison, they put it in a jar. The, after they place it down you can see someone's hand swap the jar for one containing a dead mouse. You can even hear it. (01:17:58)
Revealing mistake: When Rob is in the Cafeteria eating all the coleslaw, he yells "I'm the coleslaw king of the world!" there is a girl in the background who mouths it as he is saying it. (00:50:00)
Revealing mistake: When Will Smith throws a rock at the escaping Edgar alien, if you watch the rock after it hits the alien, it disappears after hitting the ground. (01:23:20)
Revealing mistake: When Inigo and Westley are duelling, they are making athletic jumps. One does it after the other and when they land you can see the mat wrinkle under the "dirt" on the ground.
Revealing mistake: After Carmen rescues Juni, as they fly over the city she says, "Hang on butterfingers." In the following close-ups, where is the handcuff with the broken chain on Juni's wrist? He is not wearing it on either wrist in any of these close-ups. It's obviously back in the following shots. (00:41:45)
Revealing mistake: When Woody falls out of the closet wrapped in the string lights he hears Buzz's voice, and in the next shot as Woody sneaks up to Hannah's room we see Sid's open door and doorway, which looks perfectly normal. However, after Woody rescues Buzz from Hannah's tea party they both stop in the hallway, and there's another shot of Sid's open door and doorway, only this time it's not normal to say the least. Five of the six hasps, bolts, and locks that should be (and normally are) screwed into and attached to the inside of Sid's door (one hasp mechanism, third one down from the top, is attached to the door's frame) are now actually kind of floating there in mid-air right beside the doorway, as if there's an invisible door there. Weird that Pixar artists deliberately did this, but it's bizarrely funny to see.
Revealing mistake: In the part in the motel where THING is doing morse code on the table to Gomez you can see the cut-out in the table where the guy's hand is sticking through the table.
Revealing mistake: When Charley stabs Dandridge in the hand with his pencil, he stabs the hand holding him by the neck. The depth of the wound on Dandridge's hand reveals that the pencil should have stabbed Charlie in his neck and given him a severe wound, if not kill him.
Revealing mistake: In the early part of the film, Beverly D'Angelo and Chevy Chase check into the hotel/motel. She goes in to take a shower but he barges in. If you look real closely, she is wearing underpants and is not nude although she is taking a shower.
Revealing mistake: During the scene when Cindy and the killer are fighting Matrix-style, Cindy kicks the killer, and he knocks down the book case so it falls over him. There is a vase with flowers on the book case - when it falls down the vase still remains on the book case, glued to it. (01:11:30)
Revealing mistake: When Michael Douglas attempts to swing on a vine over a deep abyss, the rock that he runs into on the other side moves like a marshmallow, indicating that it's a fake rock. (00:39:10)
Revealing mistake: In the scene where Doc Brown is following Biff into the tunnel, as Marty starts to pass between the cars on his hoverboard, one of the wheels on the rig supporting the hovering DeLorean is visible. (01:30:30)
Revealing mistake: When Carl is caddying for the priest during the bad weather, the wind is so strong that it is almost blowing them over but the trees are not moving in the background.
Revealing mistake: Near the end of the movie when everyone except for Peter dies. Lucy is supposed to be dead, but we can still see her breathing.
Revealing mistake: Mrs. Doubtfire sets herself on fire. When she jumps back and starts fighting the flames, it is obviously a stunt double as her face is longer.
Suggested correction: If you look carefully, the face looks pretty much the same, as well as the voice.
The reason the voice was the same is that it was probably an audio dub, which is a voice recording over someone else's voice.
Revealing mistake: When a baddie in a red jacket repeatedly punches Hightower, who's in the water, the fist always stops about 15 cm from his face.
Revealing mistake: When Syd and the Haitians are running, there is one shot where skid marks are visible on the road in the exact place the Haitians skid. (00:27:40)
Revealing mistake: When Hightower is in the Monster Truck you can see that a white stuntman is actually driving it in one of the shots.
Revealing mistake: When the driver is taking Amanda to the airport at the end, all the dials on the car are at zero, so obviously the car is not moving at all.