Nathan Morrow managed to sneak his donation in at the last minute to become the final person to donate to the Carry On Campaign - though he wasn't the final person to put in a request. His pick is a movie I've adored for ages, though I never quite got around to making an excuse to review it. So double thanks to Nathan.

In 2011, South Park is an institution: at fifteen seasons and no end in sight, it has not only had its obligatory "it's been on too long and running out of energy" scare but also come back around to being good again (indeed, you could reasonably argue that it's going through this cycle a second time); it has inspired a term of political commentary, "South Park Republicans"; it has turned its creators into multi-media superstars; it has reached a point of cultural saturation where even minor details from the most classic episodes are simply Things You Know, like its most obvious forerunner, The Simpsons.

'Twas not ever thus. There was a point at which the show was expected to be, and treated as, a quick 'n dirty fad, a one-joke series that would make Comedy Central a small fortune before flaring out, probably within just a couple of years of its 1997 premiere. In those days South Park was still mostly the thing it looks like to the casual observer: a crude cartoon about 8-year-olds cursing like sailors, and that sort of thing could only be stretched out for so long. Which is why the powers that be suggested that the show's creators, Trey Parker and Matt Stone, had best strike while the iron was hot, and crank out a movie while the show was still hip. The result was South Park: Bigger, Longer & Uncut, released in the summer of 1999, that grandest & most beloved of movie years in the last couple of decades, and desperate cash-in though it may have been, it was and remains a brilliant parody and withering satire, a genuinely great and completely unexpected original musical, and still arguably the high-water mark of Parker and Stone's career.

A lot of that brilliance is contextual: South Park: BLU is undoubtedly funny on its own merits, but some of the most cunning writing comes from the way it turns in on itself, on the show's reputation as a nasty-minded bit of social crudity. It is a film whose plot and entire thematic construct hinge on the impossibility of a film like this based on a TV show like that existing in polite society; and though Parker and Stone (co-writing with Pam Brady, a South Park writer in the days before Parker basically cranked out all the scripts by his lonesome) loudly and repeatedly and rightly beat the drum of "the First Amendment must not be superceded!" they also never quite deny that, when you get right down to it, this is pretty juvenile stuff. Take, for instance, the celebrated early musical number "Uncle Fucka", from the movie-in-the-movie Terrance and Phillip: Asses of Fire: an exuberant parody of the title song from Oklahoma! it's profane in the most playful, innocent way, and it's a genuinely catchy tune, and it's hilarious as hell - and when a quick cutaway shows two characters walking out of the theater, grousing about the poor taste of it, and then cuts back to the characters in a bouncy farting dance interlude, there's nothing one can say but, "Yeah, pretty gosh-darn tasteless." Are the creators insulating themselves through self-critique? Maybe a little, but I like to think of it as a gambit: by couching that moment in the film's best song (not that it was ever going to get the Oscar nomination, but it still broke my heart a little when it didn't), I see Parker and Stone as tossing a hearty "fuck off" to their critics, pointing out that potty jokes with dirty words can still be as effervescent and witty as an Ernst Lubitsch trick when they're done right. And the movie's aim is to constantly do it right, over and over again for 80 minutes; that it so largely succeeds (though it strains to fill even that running time) is not least of the reasons that it stands proud as one of the best film comedies of the 1990s.

That said, it's the cultural commentary that gives the film some actual heft, beyond being just joyously dirty (this was back in the days when Parker and Stone were able to get their ofttimes heavy-handed messages across without smothering the comedy, a problem that has frequently plagued later seasons of the show, as well as their next feature Team America: World Police). There's the obvious satire of the MPAA's fairly arbitrary rules of what movies are or are not acceptable for a wide release, in this story of how the mothers of South Park, Colorado, gin up war with Canada in response to their kids sneaking into an R-rated movie; a lesson given extra weight in the summer of 1999 when Stanley Kubrick's swan song, the cryptic, extravagantly uncommercial Eyes Wide Shut was subjected to ridiculous bowdlerisation to avoid the dreaded NC-17, while the uncompromisingly vulgar Austin Powers: The Spy Who Shagged Me skated through with a PG-13. Nor has time blunted the satire: one needs only to have witnessed the dumbfounding treatment of the insistently charming The King's Speech, the gold standard of a movie to watch with your grandma, to hear Sheila Broflovski's words continue to echo: "Horrific, deplorable violence is okay, as long as people don't say any naughty words."

And there's the self-parody of the film's own status as an animated feature, more aggressive here than in any other moment of the franchise: at times right square on the nose (a joke about crappy animation, right before a particularly stiff example of the series' iconic low-fi paper cutout-style animation, has always struck me as obvious beyond the point of sense), but also in some tremendously sly ways. It's not as obvious now as it was in 1999, for example, why the film is a musical: because in the wake of the Disney Renaissance, that's what animated movies were. A decade and change of Pixar and DreamWorks have obscured that fact, though the greater idea that American cartoons "ought" to be family pictures (a lazy notion that South Park gleefully expoldes in every frame, though it never feels obliged to call specific attention to it) remains as firmly entrenched now as in the '90s.

It's with that idea in mind that the South Park musical came to be; a travesty of specific moments from Disney's Beauty and the Beast and The Little Mermaid, host to what remains the single-best parody of Les Misรฉrables ever conceived, and in all ways a self-delighted piss-taking of the structural concerns of Broadway musicals in general; a bouncy collection of endlessly hummable show tunes that almost all have the word "fuck" puckishly jammed in someplace, just to spite the idea that musicals are what you take your kids to see - and incidentally the songs, by Parker and Marc Shaiman, are far better than they had any need to be; possibly the single most subversive fact about South Park: Bigger, Longer & Uncut is that all else being equal, it's one of the best original movie musicals in a generation.

So really, every nice thing I have to say about the movie ends up being a variation on the same idea: that it is good because it is a snotty attack on Nice and Polite things, whether it's actively pointing out that there is a gaping hypocrisy in what Americans think is or isn't okay for kids, or just flipping the bird at the conventions of middlebrow entertainment. But that's what comedy is supposed to do, really, just point out the absurdities and flaws in the world and make fun of them. Hiding their often painfully pointed wit behind deliberately shitty animation and goofy songs and silly voices is the equivalent for Parker and Stone of a fool wearing a cockscomb to insult the king to his face, a necessary function for a well-ordered society that was far too often ignored by the senseless unfunny comedies of the 1990s (in the late '90s particularly, film comedy was nearing its low ebb of the early '00s; we've recovered somewhat since then, but something as genuinely smart and genuinely funny as South Park: BLU would still be a startling, delightful surprise). The film may seem crude and obnoxious, because it is crude and obnoxious: but it's ingenious enough to not only get away with that, but to flaunt it and turn it into strength.