Somewhere between sentient feces, Helen Keller musicals, and the tale of one Scrotie McBoogerballs, South Park went from culty cable series to one of the major forces in American comedy, and its creators, Trey Parker and Matt Stone, became masters of the epic puppet action film (Team America: World Police) as well as Broadway (The Book of Mormon). But one thing remains constant: The still crudely drawn grade-school stars always learn a valuable lesson at the end of every episode, even if that lesson is something subversive or gross or politically ambivalent or, ideally, all three. “That always ends up being the last thing we put in the show,” says Parker of the moral. The lessons tend to just emerge as he and Stone write the episode, they say. Sure, they’ve taught us about gnomes who steal underpants and the dangers of being an Apple fanboy, but Parker and Stone have learned a few things themselves along the way — and they’ll be imparting plenty more wisdom when the show returns next week, on October 5.