Within the vernacular of modern show biz there exists a system of taxonomy that sounds as if it were dreamt up by a Variety editor with an annoying speech impediment: "director's director," "actor's actor," "comedian's comedian." Whatever the species under consideration, the genus is instantly recognizable as much by its implied shortcomings as by its signaled attributes. The limelight has probably been elusive for the comedian's comedian despite a white-hot talent which only the pros can appreciate and, to coin another commonplace of the industrial lingo, "hope to work with someday." Not for him is the blockbuster weekend or household celebrity. The best he can hope for is his name whispered in hushed tones, in moist magazine profiles of his box office betters; a moment of amplified applause during an embarassing cameo in some award show montage; or, now that the success of independent film is largely brokered on the success of the semi-anonymous underdog, a documentary all about his little old self...

The Aristocrats is not about a comedian's comedian, but it is about something slightly more elect and revealing: a comedian's comedy. As with any mercantile guild or philosophers circle, the closed circuit of the entertainer is worth investigating on social merits alone. Who are these people and what do they do when they're not working? Even if the answer is, Still working, what's different when the cameras aren't on? This is why old Friar's Club and Dean Martin roasts are now available on DVD and why books like Live From New York: An Uncensored History of Saturday Night Live top the bestsellers lists. It's not the ham schtick, bad haircuts, or parade of bold-faced (and mostly dead) names that fascinate us; it's the access to a rare-glimpsed culture of comity or commiseration, how those bold-faced names intimately know one another, or pretend to do, anyway. It's the cant-free chaos of shoptalk, the personnel abuse -- whether ironic and well-meaning, or sincere and irate -- that makes these spectacles no different than those of a vaguely functional family that drinks together. From scripted intentionality to failure-friendly improvisation. All certificates of inauthenticity have been voided as a little something extra for the fans. Actually, failure-friendly doesn't quite cut it: failure, and a temporary immunity to it, is the whole point. David Letterman's monologue would have been consigned to the dust-bin of Nick-at-Nite reruns a long time ago were this not true.

And this is pretty much the conceit behind a legendary inside joke of vaudeville that's been passed down through the ages and told mostly offstage as a form of self-entertainment. It's built upon the thinnest and most shiftable armatures of form, a Zen-like rock garden of humor. Ready? Here goes: A family visits a talent agent. The father tells the agent they've got this amazing, must-see act. "What is it you do?," asks the agent. Now insert the vilest, most elaborate thought-images of carnality, incest, bestiality and scatology you can dream up on the spot and sustain indefinitely. (Grandmas and newborn infants aren't just fair game, they're de rigueur.) Finish with one justifiably horrified agent who has a single follow-up question, the name of the act, and you've got the whole shebang of The Aristocrats, which is also the punchline. The same hoary set-up is told and retold and with alternating levels of gusto and flourish by everyone who's still alive and ever made you laugh. Or never made you laugh, but will do so here. George Carlin, Gilbert Gottfried, Bob Saget, Drew Carey and Cartman from South Park all spray their own brand of liquid filth to enormously hilarious effect. (That Gottfried, the Patron Saint of the Onstage Reincarnation, and Saget, who charitably donates his Frankenstein rendering of the joke to the "kids from Full House," are two of the funniest in this capacity is another testament to the you-only-thought-you-knew world of professional stand-up.)

You might say that such a documentary, which is the badly molested brainchild of Penn Jillette and Paul Provenza, depends on a one-trick pony, but given what ponies are rhetorically put through for two hours, you'd only court banality with that description. Instead, what's been produced here is a very smart and engrossing work of history, deconstruction and reconstruction of a near-Iliadic text by academics you wouldn't mind reading even when they do get a touch pedantic. I suppose it was inevitable that the gender and race distinctions of "blue" comedy would get its exegesis, but even this is handled skillfully by Chris Rock, Whoopi Goldberg and Phyllis Diller, charmingly buttoned-up about the obscene, all the while wearing a muu-muu. "I fainted the first time I heard it" -- which leads you to wonder what poor Phyllis must have made of Sarah Silverman's exquisitely tasteless interpretation of the bit, ending in the slow-dawn realization of her own rape.

A few years back Jerry Seinfeld made a documentary called Comedian. The problem with that compulsive peak behind the curtain was that it attempted to take a wildly inordinate success story -- about the richest and most high-profile master of observation, ever -- and boil it back down to its humble, on-the-road essences. The duds remained duds because of a complete lack of self-consciousness about them, not to mention a too-literal presentation of the agonies of invention by a mediocre supporting cast. Whereas with The Aristocrats no one hogs the mic, if only because of the deliberately thankless material everyone has to work with. That's the fun. Small and formulaic imperceptibly building to outsize and unpredictable climax is also one definition of artistry. Indeed, it says more about the true nature of comedy that a shit-soaked, uncle-fucking mongoloid girl of seven somehow represents the more attractive side of an industry filled with bank-breaking personality disorders like Jerry, and self-obsessed primadonnas like Orny Adams.