Revealing mistake: While Biff and the others are chasing Marty on the skateboard, when Marty grabs a green truck the stunt man is doing it for him.

Back to the Future (1985)
21 revealing mistakes - chronological order
Directed by: Robert Zemeckis
Starring: Christopher Lloyd, Michael J. Fox, Lea Thompson, Crispin Glover, Thomas F. Wilson

Continuity mistake: When Marty chases after Biff on the borrowed 'skateboard', Marty is wearing a dark grey belt and a red/blue print shirt under his red/beige jacket. However, when Marty is hanging on to the front of Biff's car as they turn a corner (and in another shot), Marty (stunt double) is wearing a light brown belt and solid tan shirt. (01:07:00)
Dr. Emmett Brown: Don't worry. As long as you hit that wire with the connecting hook at precisely 88mph the instant the lightning strikes the tower... Everything will be fine.
Question: Right when Marty gets back to Doc before he goes back to 1985, he's praising his dad's actions of the night. One line that's bothered me ever since I can remember is "My dad laid out Biff. He's never stood up to Biff in his life." And then the Doc pauses for a second and gets a strange look on his face and says, "Never?" To that, Marty says, "No, why?" and the Doc shrugs it off saying, "Nevermind." What's Doc thinking? The best I can come up with is that he's wondering what effects it'll have on the future, but that's a rough guess. If anyone out there knows, I'd be happy to hear it.






Chosen answer: I think that is *exactly* what he is thinking. He realizes that by standing up to Biff, George may have irrevocably changed his personal future, and therefore affected Marty's future as well. This is exactly the sort of thing Doc was so eager to prevent by refusing to hear any information about the future.
Phil C.