Jennifer: Excuse me, Doc Brown. I brought this message back from the future and, well, now it's erased.
Doc: Of course it's erased.
Jennifer: But what does that mean?
Doc: It means your futures haven't been written yet. No one's has. Your future is what ever you make. So make it a good one, the both of you.
Doc: Clara was one in a million. One in a billion. One in a googolplex!
Young Doc: Remember, where you're going, there are no roads.
Marty McFly: You're the doc, Doc.
Doc: This'll shoot the fleas off a dog's back at 500 yards, Tannen! And it's pointed straight at your head!
Clara Clayton: I don't dance very well when my partner has a gun in his hand.
Doc: And in the future, we don't need horses. We have motorized carriages called automobiles.
Saloon Old Timer: If everybody's got one of these auto-whatsits, does anybody walk or run anymore?
Doc: Of course we run. But for recreation. For fun.
Saloon Old Timer: Run for fun? What the hell kind of fun is that?
Engineer: Is this a holdup?
Doc: It's a science experiment!
Marty McFly: Listen, you got a back door to this place?
Bartender: Yeah, it's in the back.
Buford: 8 o'clock Monday, runt. You ain't here, I'll hunt you and shoot you down like a duck.
Gang Member 1: It's dog, Buford. Shoot 'im down like a dog.
Marty: Clara Clayton was supposed to die in the ravine. All the teachers tell the kids a story about a schoolteacher named Clayton who died in the ravine, and all the kids in town remember it because they all have a teacher they'd like to fall in the ravine.
Young Doc: All you have to do is drive the time vehicle directly toward that screen accelerating to 88 miles an hour.
Marty McFly: Wait a minute, Doc. If I drive straight towards the screen, I'm gonna crash into those Indians.
Young Doc: Marty, you're not thinking fourth dimensionally. You'll instantly be transported back into 1885, and those Indians won't even be there.