There's only one person Marty can turn to for help. So he barges into Lou's café, uses the phone in the back to try calling Doc (who doesn't ever seem to be home), then procures his friend's address, so he can at least track him down that way.
Before he skedaddles, however, he bumps into a couple of other familiar faces—Biff, and his father-to-be, George McFly.
Turns out their relationship has been consistent over the years. George is giving Biff his homework to copy, because Biff has been a bully from day one.