Shortly before last night’s season finale, South Park was renewed for three more seasons. So much for the speculation, which the mid-season finale “You’re Getting Old” set off, that Parker and Stone were getting tired of the show. The other thing people started wondering when that episode aired is whether they were going to shake things up, stop relying on formula, and create some more story arcs and continuity. Of course that didn’t happen; the follow-up episode turned out to be a great big meta-episode about how franchises can become tired and stale, and it ended with a big meta-gag about pushing the reset button and bringing everything back to the way it was, because it’s easier. Since then, the ideas introduced in that two-parter – Stan being an embittered middle-aged kid; Stan’s parents reaching the end of their tether; Kyle and Cartman becoming friends – have been abandoned. Which, really, is the way it should be; South Park is a show where every episode is a hastily-produced excuse for Trey Parker to talk about whatever is on his mind, and a show with continuing characters can’t do that unless it’s grounded in a formula. There are certain constants, mostly having to do with characterization or who the main characters are (and even that can be abandoned, since there’s at least two episodes where none of the four main boys appear), and everything else is completely negotiable from week to week. If the events of one episode or two-parter bled into the events of the next one, then actions would have consequences, and Parker would have less freedom to get stuff off his chest. Some might consider that helpful – more character development, fewer references to reality shows – but that’s not what South Park is or was.
The closest the show ever really came to doing a real continuing storyline was in the sixth season, where Kenny was really dead for most of the year. There was something resembling a story arc: Kenny’s dead, his soul is trapped in Cartman’s body, the boys pick and then reject Butters as their new fourth friend, and pick Tweek as his replacement after (naturally) a reality-show parody. That’s as far as South Park has ever gone in the direction of making one thing lead to another. Otherwise, when they have continuity it’s usually almost a gag about continuity: a reference to a previous episode becomes a joke in itself, because most of the things that happen are forgotten instantly. Kenny is the source of a lot of these gags, where they try to explain why he can die and then come back. The idea that this is his superhero power, and that this is both a blessing and a curse that he alone has to deal with, is not a serious thing that is addressed again next week; it’s a parody of superhero comics, first of all, and second of all it’s a joke they can go to when they need it. (I personally find Kenny funnier as the dirty-minded member of the group – the only one of the four boys who isn’t a total innocent about sex – than the superhero parody. But Parker and Stone have always been annoyed by his inability to speak clearly, and they like to get him out of the hood and talking un-muffled English.)
Update: As noted in comments, Mr. Garrison’s sex change was another experiment with continuity, and so was his replacement as the boys’ teacher. All of that was eventually reversed, but it was there. Though Garrison has lost his position as the most-featured adult character on the show since he went back to being a guy; Randy has taken over most of the stories meant for grown-up characters.
I don’t think the show is at its best these days, though the nature of it is that it’s always going to be uneven: for all we know, the next three seasons could produce some great work, since the quality of an episode depends on whether the story idea is interesting enough. But I do feel, watching an episode like last night’s, that there’s only so much they can do to keep the formula fresh. (It’s been a while since they introduced or promoted a character who could freshen things up; Butters provided a shot in the arm for the writing, and so did the increased number of stories for Randy – further proof that Hollywood writers are most comfortable writing for a dumb middle-aged husband whose wife inexplicably doesn’t leave him. But it’s been years since they came up with something like that, so we mostly get stories about Cartman being an idiot and causing massive carnage.) But the lack of continuity and consistency is just part of the style, except for that very brief flirtation with the idea in the sixth season.