when creating an oc (or multiple) it's important to establish their relationship with all of the characters, especially in a movie like it where there are so many! here are some friend tropes to play with and personalize for your oc:

befriending the enemy — some characters are black and white when it comes to their role in the plot, in this case it's the good guys and the bad guys. other characters ask, "why are we enemies anyway?" has anyone ever tried talking things out? maybe if they got to know them a little better they might even turn out to be a decent person. so they try it out.

friendly rivalry — not all rivalries are bitter. some are competitive, with both parties being driven by a healthy desire to one-up each other and, regardless of the outcome, they'll continue to push themselves in anticipation of their next eventual showdown. as such, they develop a mutual respect for each other's talents, even in defeat. this can be demonstrated by playful banter, mocking one another, and *several* eye rolls.

better as friends — this trope is for when something romantic happened once but won't happen ever again. two people date for a while (or maybe just hookup), but then realize they're better as friends, and use this as their excuse when asked. of course, sometimes this leads to unsolved sexual tension, which can be a direction that you can go into with your story if you so please.

like brother, like sister — sometimes, two characters of the opposite sex are very close. so close that you might expect them to be dating. except they're not. they admit that they matter a great deal to each other, that they would die for each other, that they can't imagine life without each other. they aren't just any pair of friends. they're as close as family. they're like brother and sister!

the friends who never hang — naturally a large cast allows for several different smaller pairings within the larger grouping. this mixing and matching allows for the audience to see the interconnectivity of each of the characters' lives on one another (take eddie, bill, and richie for example). it also allows for different storylines to showcase how one character may relate to another by giving them their own subplot. but then there are those two characters within the same group of friends who almost never seem to hang out.

romantic two-girl friendship — at the beginning of adolescence, there is a time when friendship is emphasized, usually junior high or middle school. these friendships can have very strong emotional bonds, and, when two girls develop a close bond, it will almost appear to be a romance. they hold hands, getting together to do something is a "date", fights are treated as a "break-up", they're willing to sleep next to each other in the same bed (and maybe even cuddle). they're also sometimes capable of moving and speaking in perfect unison. they may not actually be in a romantic relationship, but it is emphasized in such a way that if they were, you'd assume it'd look this way. this can lead into a real, romantic relationship if you sprinkle in some questioning sexualities and passionate kissing.

friend vs. lover — this is when a character's best friend and the love interest have a rivalry over "ownership" of the third party. both usually start a secret war for the affection and attention of the third party, trying to slander the other while seeming innocent. by the end, one or the other usually reveals they were less than ideal as a friend or lover and get cropped out of the picture. or, better yet, they reconcile their issues.

hope this helps!
(gracie)