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 Henry hits one of the corrupt cops in the head with an otoscope it bends off his head like rubber.
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: After Clark cuts the rope on the large tree, it spreads out and branches start breaking windows. One of the branches has a pole of some type pushing it through the window.
Revealing mistake: During the first shot of Larry being pushed out of the car, it's blatantly a stunt double who is taller, thinner and has shorter hair than the actor.
Revealing mistake: In the scene where they have just had sex, Meg goes to get out of the bed and is supposed to be naked, but when she puts on the bathrobe you can see she is wearing some type of slip or nylon panties.
Revealing mistake: On the way to the party, near the end, they are supposed to be in Alabama when the car gets pulled over, but the officer's badge, shoulder patch, and car all say Georgia State Police. (00:51:45)
Revealing mistake: When Nick is being sucked out of the hole/cave, you can see the wires visible from his waist. (01:20:35)
Revealing mistake: When Molly's mother is listening (to what she thinks is sex) outside the apartment door, the handle is shown on the right side of the door. But anytime after that the door opens from the left side. Both doors open on the left. (For some reason Molly has 2 front doors to her apartment).
Revealing mistake: In the celebration scene at the end, there are multiple times when you see huge sections of the stadium with no people in them. The most obvious is when WMH jumps into Jake's arms. (01:39:05)
Revealing mistake: When the plane crashes in the tree the wires holding it are visible. (00:17:55)
Revealing mistake: During the Hy Brasil sinking sequence you can see a horizontal line in the water in the background, this is the edge of the water tank they used to film this sequence. It's also visible in several shots from the longship.
Revealing mistake: When Ray, Winston and Egon are underground looking for the river of ooze, there is a scene where they break down a small wall of rocks. Ray then sits on one of the rocks and it bends under him - it's rubber or foam. (01:01:50)
Revealing mistake: In the shot where Barbara is cartwheeling down the stairs after Oliver wrestles the ornament from her in the previous shot, the stairs have become totally flat like a ramp.
Revealing mistake: After Art and Ray successfully blow up the Klopek's house, Ray emerges from the ruins and the porch collapses behind him. It can be seen that the porch supports are dragged backwards towards the house to allow the porch to collapse behind Ray.
Revealing mistake: When Larry and Richard are dragging the two bodies to the closet the first one lifts up his legs for Richard to put him in.
Revealing mistake: In a shower scene, the camera moves to a point which allows us to see the shorts that Dexter is wearing to keep his modesty.
Revealing mistake: When Eddie shoots the cashier at the Wady liquor store he falls backwards into a shelf with whiskey bottles. You hear some bottles break and see some splinters flying, and then there comes a Niagara-style whiskeyfall pouring over the shelf that must have come from a large reservoir behind. (00:30:40)
Revealing mistake: When Dave and Walley are running with a car, Walley says that he heard some shots. Dave replies that he didn't hear anything, but as you know Dave is deaf, and he reads Walley's lips each time he speaks. In this scene, he wasn't looking at him, but answered. (00:47:45)
Revealing mistake: When Cash stuffs the grenade in the trousers of the guy with the ponytail and throws him down the stairs, you can see that the explosion doesn't come from the grenade but from the hall on the right side of the stairs.