Plot hole: R.J. Fletcher is shown as a ruthless businessman who knows everything there is to know about Channel 62 - who owns it, how much it's worth, who is running it, the financial troubles it is having and so on and so on. He is also fully aware of the telethon and the fact that George is selling the station as a going concern for a total of $75,000.00. It is simply asking too much of audience credulity or 'suspension of belief' to think that such a hard-headed businessman would not work out that he could, using stooges, buy a controlling interest in the station for $37,501.00, saving himself a small fortune and closing the station down over the objections of his minority shareholders. Something this blatant could not possibly be a character mistake - he is already planning on buying the station for the full price (from Big Louis) so don't tell me he wouldn't just switch plans and buy it from George instead!
Other mistake: Beethoven didn't seem fussed nor resentful of Napoleon being part of the group. Historically he temporarily admired him and wrote the Third Symphony inspired by Napoleon's ideals of Europe's new hope of enlightenment but later despised him after he crowned himself Emperor of France in 1804 and furiously scribbled out his name off the title page of his Third Symphony and named it Eroica which he originally titled it as "Bonaparte Symphony" due to his former admiration of Napoleon.
Continuity mistake: In the bowling alley, 'Pal' comes over to speak to Tia. During their conversation, the camera pans to Maisie throwing a bowling ball; however Tia is now sitting alone. Pal has disappeared. (00:40:10)
Character mistake: The sign for the hotel where Jake is staying at in Mexico says Tengo Quarto's para Renta. The word is spelled wrong. It should say CUARTOS. Also, there is no apostrophe s in cuartos. It is plural, not possessive.
Other mistake: Dr Anne wets her dress by dropping water on it, but her dress is dry afterwards. (00:54:00 - 00:55:30)
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)
Factual error: In the scene where Clark is working on the lights the full moon is shown. This is December 14th according to the advent calendar. On December 24th when Santa's sleigh goes sailing over the moon, it is still full.
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.
Continuity mistake: During the first car ride scene Harry is spitting the seeds out the window. One of the shots shown of the car from the outside shows the window still up after he has rolled it down.
Continuity mistake: When Philip surprises Alex and Corrine undressing in the living room, Corrine throws her panties in the air and they land on Philips' head. Philip pulls the panties off his head and throws them down. After a quick cut to the surprised Alex and Corrine, the camera cuts back to Phillip with the panties magically back on his head.
Other mistake: When Stallone stops the bad guys in the semi full of cocaine, they fly through a windshield that is apparently made of plate glass, and not the safety glass found on almost every other vehicle windshield on earth.
Factual error: Hooch is a french mastiff. The dog he gets pregnant is a collie. Different breed dogs do not make purebred puppies. Hooch's pups would be part collie, part mastiff. In the end of the movie, one pup is pure mastiff like hooch and 4 are pure collies like their mother.
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.
Visible crew/equipment: In the scene where John Travolta is racing Kirstie Alley to the hospital, there is one shot where a camera rigging is clearly seen mounted on the hood of Travolta's taxi in the reflection of the storefront windows.
Continuity mistake: In the scene where Belushi and Jerry Lee (the dog) enter the warehouse, Belushi askes everyone to stop what they are doing and even has the forklift driver lift him up so he can talk to them. Once he is done talking, he tells the lift driver to bring him down. The next few shots where they show Belushi walking to his car, if you look closely, you will see that the fork lift is back up in the air, but there were no sounds and there isn't another lift to be found. (00:25:05)
Continuity mistake: When Eddie tells Homer about the Wady robbery while they're driving along, there's a change from broad daylight to late dusk in mid-sentence. (00:33:05)
Other mistake: When Tom Hanks is walking down the stairs a chainsaw comes through the wall. If you look at the wall a second earlier you can see a line where the chainsaw is supposed to come through.
Continuity mistake: Towards the end of the movie Dave takes Walley's jacket and uses it to help them slide down a cable. Before they slid down, Dave tells Walley to hold on, and Walley asks if they're going to be above the ground. Dave tells him no, and off they go. However, Dave is deaf, and reads lips, and Walley is standing behind him when he asks the question. So how did Dave read his lips if he wasn't looking at him?
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)