is asking about the fanon. Everyone else is too. Well here's mine.
1) John once met a woman who he could have really loved. She was exactly the same as Mary, except for her hair was darker and green eyes. The problem was that she looked too much like Dean.
2) Sam only liked school because Dean hated it.
3) Dean only drinks alcohol with Spanish sounding names because his mother had always wanted to go to Mexico. It was the only secret she ever kept from John, but told Dean.
4) The Winchesters never wear shorts. Not because of their scars, but because they never can find a decent pair that would fit Dean, and then Sam. John couldn't afford to buy them individual pairs of jeans, let alone shorts.
5) Mary's father bought her the Impala when she was 17. She had wanted a mustang like her best friend Kelly, and the Impala was cheaper. She named it "Sally" because she knew her future husband would not want to call her car "Steve".
6) Sam knows that he looks like Jared Padalecki from Gilmore Girls. If he was scrawnier, shorter and had a bad haircut, they would be perfect twins. The sad thing is that Jessica thought they were identical.
7) Dean's favorite show is and will always be Knight Rider. He secretly wants his car to talk to him, especially when Sam went away to college and Dad went off to wherever. He is not a Hoff fan, even if that's the name his credit card is assigned to.