1:
Stan and Kyle would definitely sneak into each others room at night to have a sleepover lol (this is actually shown in the show when Stan hears a knock on his window and says "Kyle?", S:8 Ep:6 *i think*)
2:
I feel like Craig and Stan would be cousins there is no evidence to support this but it's pretty cool.
3:
Eric would definitely listen to early 2000s pop music. (He has sung some songs from the early 2000s and 1990s at least the songs sound like it)
4:
The main 4 would argue about who would pay for the stuff when they go out to eat or go to the mall and they would end up getting kicked out the place.
5:
Wendy and Bebe are best friends so they came up with a plan to date Stan and Kyle because they are close also. Wendy and Bebe could do a lot of things with them and nobody would be bored (they attempt this or wanted to date them *Wendy with Stan and Bebe with Kyle*)
6:
Stan would watch horror movies and talk about them to Kyle but Kyle would try to change the topic. (Also shown in the show that Kyle hates horror movies.)
7:
Butters would make tiktoks about how to stay out of trouble when he moved out of his parents house. (He just wants to help kids.)
