Continuity mistake: Notice Marty's hair in the scene when he's playing "Johnny B. Goode." It's quite larger than when he says, some seconds later, "I guess that you're not ready for it yet." That's because when he says that, it's a recycled shot from the original BTTF, whereas most shots showing he's playing the guitar are newly made for BTTF2. However, Marty's hair is considerably longer in the new shots. (01:27:19)
Continuity mistake: When Spock, wearing rocket boots, is in the turboshaft carrying Kirk and McCoy on either arm, he fires the booster rockets, thus propelling the three of them up the turboshaft. If you watch carefully, the deck numbers in the background as they rise upwards go as follows: 35, 52, 64, back to 52, 77, 78, and then 78 again! Not content with one goof, Kirk and McCoy can quite clearly be seen with their feet dangling in mid air, not on Spock's boots. They aren't exactly clinging to him either, more like leaning against him. Surely Kirk and McCoy would be unable to hold onto him!
Continuity mistake: Early in the film Bud throws his wedding ring down the latrine and then retrieves it with his right hand so it is covered with the blue disinfectant. In a (much) later scene, Bud has a blue right hand, despite not having had one in the intervening period. (01:44:48)
Continuity mistake: When Vigo throws the streams from the proton packs back onto the Ghostbusters, there is a wide shot of Egon getting thrown way over to the right. However, when they do a closer shot, he is way over to the left, closer to the other three Ghostbusters. (01:33:50)
Continuity mistake: When Andre Toulon puts Blade into the suitcase, near the start of the film, Blade's hook is on his right hand but it is attached to his left hand in all other shots of him. (00:09:45)
Continuity mistake: When Amy is in the kitchen cleaning, she starts mopping the floor, then dancing with the mop held upside down. The mop starts out wet, but when she's dancing it's dry (either that or she would be getting dirty mop water in her face while the mop is being flung around).
Continuity mistake: At one point, when they time-travel away from "1,000,000 B.C.", Bill is on the left inside the phone booth and Ted is on the right. When the camera switches away, then back, they've changed sides.
Continuity mistake: When Wallace races to get crackers, check the packet's logo. When the camera angle changes it's different. (00:08:57)
Continuity mistake: When the devil sets Toxie on fire, there's a group of five people standing there with empty buckets. But in the next shot the buckets are filled with water.
Continuity mistake: After the shock waves, Snyder says he has a 'fire over here.' You see Scarpelli putting out the fire with a fire extinguisher. The hose is attached to the extinguisher, but a short time later she is holding the hose in her hand, then in the background a short time later you can see her, and the hose is again attached to the extinguisher.
Continuity mistake: Sherman helps Louise put on her uniform from the back, but the zipper is in the front. When she turns around, no seams/zippers/etc. appear on the back of the uniform. This takes place just as she gets out of the shower.
Continuity mistake: In the abandoned building in the jungle, a man is holding a chain in one hand and an iron ball in the other. The ball appears or disappears depending on the angle.
Continuity mistake: When Banner changes into Hulk in the subway station, his beard is gone. When Banner changes back after his "Hulk-out" his beard is back. (00:16:00 - 00:18:00)