I admit it: I was one of those who did not think South Park would be sustainable. After the breakout success, the immediate product sell-outs, the audaciously early feature film and a standard of blazing originality set higher with each episode, you’d be forgiven for thinking that South Park would burn out its fuel after two years, maybe three.

Time makes fools of us all, and Trey Parker and Matt Stone have clearly silenced anyone who saw them as one-note frat boys making cartoons with dirty words. South Park has become a perpetual motion machine, a bulb that shines more brightly the longer it stays on. Maturity looks good on an immature show, and the latter-day episodes offer much tighter scripts and sharper satire without forgetting the non-sequiturs and creative vulgarity that always made us laugh.

The sixth season DVD set is a blend of the crude and topical All levels of offensiveness are represented, from small-time stuff like name-calling, to the sublimely ewww, like a berserk liposuction, people crapping from their mouths, Shelley’s tidal-wave period, and Cartman collecting semen by…yeah. But season six also expands its satire of touchy events and issues of the day. As usual, nothing is off-limits.

So: this is the season without Kenny, for a while. He has been replaced by Butters, emerging as a lead character after years in the background. But he is soon to be supplanted by Tweek as Stan, Kyle and Cartman’s friend no. 4 in a Bachelor-style elimination show. The adorable wet blanket Butters channels his humiliation to become…the abominable Professor Chaos. Some other new faces this season include Mr. Slave, leather-clad boy toy to Mr. Garrison, and Lemmiwinks, the gerbil who goes on a quest through Mr. Slave’s intestines. Twong Lu Kim, owner of City Wok and builder of City Wall, just about completes the list of stereotypes this show has compiled.

In keeping with other South Park collections, the creators deliver mini-commentaries over each of the 17 episodes, four or five minutes apiece. They’re shorter than in previous seasons, supposedly because viewers got bored with them. And I can believe that a viewer who doesn’t know that he can TURN THE COMMENTARY OFF at any time would have a short attention span. Whether you approve of the commentaries or not depends on how much insider information you want. Some amount to redundant descriptions of the episode or offer the phrase "we just had this idea" and leave it at that, but most try harder. Trey and Matt talk about the origin of City Wok, the real-life stories behind "Bebe’s Boobs Destroy Society" and "The Simpsons Already Did It", and Steven Spielberg’s reaction to the "Free Hat" episode. Some technical details work their way in: how the staff reacted to outrageous scenes, how the creation process changes throughout a season, how a song was recorded, how no one in six years had ever drawn a side-view of Chef.

The image pixilation is very obvious, and with South Park’s cut-and-paste animation style, some shapes and lines appear jagged. The sound is nothing spectacular, nothing to complain about. I don’t consider ads for other DVDs to be true special features, but Comedy Central has included full scenes from Drawn Together, Reno 911, and a Patton Oswalt stand-up video along with its trailers. That’s a pretty smart way to do promotion and give the buyer something substantial.