Rasputin: You dare to banish the great Rasputin? By the unholy powers vested in me, I banish you, with a curse! Mark my words: you and your family will die within a fortnight! I will not rest until I see the end of the Romanov line forever.
Dr. Emmett Brown: Tell me, "Future Boy", who's President in the United States in 1985?
Marty McFly: Ronald Reagan.
Dr. Emmett Brown: Ronald Reagan? The actor? Then who's Vice President? Jerry Lewis? I suppose Jane Wyman is the First Lady!
Marty McFly: Whoa! Wait! Doc!
Dr. Emmett Brown: And Jack Benny is Secretary of the Treasury.
Marty McFly: Wait a minute, Doc, are you trying to tell me that my mother has got the hots for me?
Dr. Emmett Brown: Precisely.
Marty McFly: Whoa, this is heavy.
Dr. Emmett Brown: There's that word again; "heavy." Why are things so heavy in the future? Is there a problem with the earth's gravitational pull?
Dr. Emmett Brown: This sucker's electrical. But I need a nuclear reaction to generate the 1.21 gigawatts of electricity I need.
Marty McFly: Doc, you don't just walk into a store and buy plutonium. Did you rip that off?
Dr. Emmett Brown: Shhhhhh. Of course. From a group of Libyan nationalists. They wanted me to build them a bomb, so I took their plutonium and in turn, gave them a shiny bomb-casing full of used pinball machine parts!
Doc Brown: Now, if my calculations are correct, when this baby hits eighty-eight miles per hour, you're gonna see some serious shit.
Dr. Emmett Brown: Now, remember - according to my theory, you interfered with your parents first meeting. If they don't meet, they won't fall in love, they won't get married and they won't have kids. That's why your older brother's disappearing from that photograph. Your sister will follow, and unless you repair the damage, you'll be next.
Marty McFly: Sounds pretty heavy.
Dr. Emmett Brown: Weight has nothing to do with it.
Marty: Doc look, all we need is a little plutonium!
Doc: Oh! I'm sure that in 1985, plutonium is available at every corner drug store, but in 1955 it's a little hard to come by. Marty, I'm sorry, but I'm afraid you're stuck here.