Obviously these are all just first thoughts and suggestions, I'd love to hear what you think as well, since of course you know your own characters better.
@nodogsJack: Billy would have been insistent on staying in her ever shifting circle of friends. I'll leave it to you how she took that.
@banjoanjoSara: Freshman year, Billy for his part is still transitioning from church going band geek to goof-off theater kid. They were dropped off at the mall by their respective parents(maybe her brother was secretly tasked with keeping an eye on them, under the guise of hanging out with his own friends). There just wasn't any chemistry, maybe this is when Sara started to realize she wasn't into guys.
Billy's parents asked "what happened to that nice Sara girl?" for years after.
@Salsa VerdeMier: Billy would be decent to him, but probably didn't have a lot of interest or common ground to form any real friendship
@PriskNatalie: Billy was well liked, but in high school that's not the same as
popular, and for the most part they didn't really move in the same circles. They
did, however, follow each other on Instagram, and actually still do(though, for his part Billy is only vaguely aware of the fact).
@BenzaitenMelanie: Billy and Melanie seem to be pretty self involved, but in very different ways. I think they likely had very little to do with each other, though Billy probably attended exactly one(1) dungeons and dragons club session.
@AeolianOleander: I think Billy would have taken kind of a shine to him, but probably expressed it through a lot of teasing and good natured jokes. If Oleander put up with this long enough, Billy probably would advance to openly flirting in senior year(when Billy at least was out as pan at school).
@udonoodlesMarco: If you allow, I can see Billy being one of Marco's few close friends, at least until Marco started to kind of drop off. Unfortunately, Billy probably didn't keep up with him as well as a friend should(granted, senior year and after graduation he definitely had his own drama going on).
I can see a friendly rivalry through underclass years, them being two of the school's biggest musical talents.
@LaertesDante: Is there any chance he was in Billy's high school band?
@RocketteSamuel: I think at the very least they would have shared cigarettes, but Billy is relentless when trying to be friends with someone. You can tell me how Sam felt about that.
@The Man EmperorTrystan: I don't think Billy likes him very much, but more than anything he would just stay out of his way.