Pick a BTTF character, and pick five things that never happened to them. They could range from plausable (things that actually might happen to them in another universe) to the implausable (things that completely contradict the character's personality).
I'll pick... Dr. Emmett Brown:
1. He never reads Jules Verne at the age of eleven, and never takes up science.
2. Not wanting to lose the girl of his life, he reluctantly take on one of the three projects - and ends up marrying Jill Wooster.
3. Feeling that he's not entirely accepted in Hill Valley, he ends up moving to another town - and tries to change his image.
4. Even after being visited by Marty for a week, he decides not to invent the time machine. Therefore, he never finds out about Marty's future. So Marty races Needles, and breaks his hand.
5. Tired of being a "constant failure" with his science experiments, he decides to give up on science altogether.
Five things that never happened to Marty:
1. He never burns the living room rug at the age of eight.
2. He never meets Doc, so he never goes back in time.
3. He never starts his band, which made him never send his audition tape.
4. He never goes out with Jennifer, which makes Marty Jr and Marlene cease to exist.
5. He comes to school on time everyday and never gets in trouble with Strickland.
Five things that never happened to Jennifer:
1. She actually dies upon fainting, creating a massive paradox. (One theory I question, BTW)
2. She becomes Needles' girlfriend, and intensely dislikes Marty. (Strangely enough, some fics do pair her up with Needles or the Tannen of the generation - usually in alternate realities where Marty doesn't exist.)
3. She becomes a prostitute to support herself. (Actually, that very well could happen to her in 1985A.)
4. Doc and Marty forget about her, leaving her in 2015 - only to have the thirty year older Marty find her and take her in. (Pretty much the reverse of Marty being left in 1955.)
5. She gets a role on Family Ties, and becomes Michael J Fox's future wife.