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 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)
Continuity mistake: When the SR-71 is taxiing from the hanger its tail number is 17964, but just before the plane explodes the tail number is 17974. (01:25:15 - 01:31:30)
Visible crew/equipment: During the final battle, when the Ewoks swing on the ropes, a crew member's hand is visible pushing one of them forward.