Continuity mistake: In the scene in the basement, Chunk is about to drink from the water cooler bottle that is mostly empty. When he stands up and tries to catch it, it's more than half full. (00:40:25)
Continuity mistake: When Marty arrives in 1955, he lands on Peabody's farm and rams through the pine tree he then hits a scarecrow which flies over the top of his car. Then as they show it from the inside the scarecrow slams into the windshield - but how can it slam into his windshield if it is already over the car? (00:31:30)
Factual error: The word 'magician' is spelled 'magicinan' on the cart when Nicholas bends down to collect the spiders web. (00:50:30)
Continuity mistake: When everyone is searching upstairs and Miss Scarlet and Colonel Mustard start screaming, they all come running down. Yvette and Miss Scarlet have on flat black shoes, but right after the running shot is over, both are back in heels.
Continuity mistake: When P.W. is escaping certain trouble somehow his handle bar comes off (with ribbons) a new one is replaced (without ribbons) - cool bike huh? But in the next scene the new handle has ribbons... (01:13:00)
Revealing mistake: During the scene when Audrey is having a nightmare about eating too much while on vacation, the nightmare ends with her inflating like a balloon from all the food. Her blouse splits open and down the middle, where the buttons have broken, the dark balloon used for the effect is visible. (00:16:35)
Continuity mistake: When Vernon is looking in the basement files and Carl walks in, the card in the drawer label holder is tilted and it stays this way for a few shots. When Vernon claims it's a highly sensitive area, the card is now straight, but in the shot after that it is tilted again.
Continuity mistake: When Jerry has Charley pinned to the cracked bedroom wall by his neck, he suddenly drags him over to the window a few feet away - which is nailed securely to the frame - and lifts it up effortlessly. Next, we see Charley looking over to his right side, but now he's back up against the cracked wall in this shot, not a window. (00:29:50)
Continuity mistake: When the paperboy comes around to collect his $2.00 plus tip, Lane keeps the door only open a crack. But when it switches to shots of the paperboy not only is the door wide open but the color has changed from blue to white. (00:22:00)
Continuity mistake: Lisa is trying to convince Gary's parents to let him go to the party. There is a glass of beer on the table. The camera switches to a close up and then back to a wide shot and the beer is gone. (00:37:49 - 00:39:10)
Continuity mistake: During the scene where Fletch is at the hospital trying to locate Stanwyk's medical records, he drops lots of files on the floor and asks a nurse to sort them out. When he is talking to her he has a stethoscope in his ears, but when the camera moves behind him they are suddenly round his neck. Moments later they are back in his ears. (00:18:10)
Continuity mistake: When Tina runs up the stairs and then falls through, she lands on a blanket but when she stands up, the blanket is gone.
Continuity mistake: When the lads run over the fire hydrant in Jonathan's father's Studie, the bumper appears undamaged. However, when they pull up in front of his house, the right side of the bumper is badly crumpled.
Revealing mistake: You see Scott walking towards the shower and he says hi to Chubby while passing him, but if you look closely after that you can tell Scott's only wearing a mask and his shoulder is bare skin. (01:00:15)