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!
Continuity mistake: The batting order in the one-game playoff is Taylor-Dorn-Cerrano (as seen in the 7th), with Hayes batting before Taylor (as seen in the 9th). Cerrano hits the homer with two outs in the 7th, and Hayes is shown batting with nobody on, and two outs in the 9th. If they faced the minimum, Hayes would've been up with only one out (#5 batter gets the third out in the 7th, 6-7-8 batters get out in the 8th, and the #9 batter gets one out before Hayes). There's no way they could've gone through the line-up again without scoring a run. The furthest they could've gotten was the #8 batter (two spots before the leadoff Hayes) coming to bat in the 9th with two outs and nobody on. (01:23:30)
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: 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.
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.
Continuity 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.
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.
Factual error: In the beginning sequence where they show the sperm first fertilizing the egg, it is biologically incorrect - only the head part of the sperm enters an egg, everything else stays on the outside and eventually dies off.
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: 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)
Factual error: While Fletch is riding with the bikers, they stop at a stop sign where a family in a station wagon roll up their windows in fear. A sign at a service center in the background is the Castaic Junction, which is in the greater Los Angeles area. The movie is supposed to be taking place in Louisiana. (01:12:35)
Continuity mistake: Ruth's pink checklist never looks quite the same throughout the movie. When she crosses "FAMILY" off her list, her line is crooked, but the next time they show the list, that line is very neat and straight. You can also see differences in the circles that she draws around the numbers. Sometimes the circles intersect the dashes, and sometimes they don't.