When Did The Handling Of The Boys Ensemble Shift, Exactly?
So, I've gotten into and been going through episodes of the series of the series for the last month or so, and something that's jumped out to me is that there's a pretty hard shift in the stretch of Seasons 11-17 where the show pivots from treating the OG four boys as the "core" cast, with the other boys in Garrison's class just being kinda there, to treating all of them collectively as a larger friend group, most obviously in the scenes of them talking in the cafeteria. Stories of just Stan/Kyle/Cartman/Kenny still exist, but they're scattered at best, and a lot of them incorporate Butters as the fifth member without any need to justify to (and in a few, he replaces Kenny outright).
Anyone able to identify when exactly this shift started? Because it's really interesting to me as part of how the series has developed as a whole.