For comedians, "The Aristocrats" is their funny valentine. Or filthy valentine. Or both.

Bob Saget

"The film, as crazy as it is, is a love letter to comedians and comedy and all the different ways they improv around something," says Bob Saget. His career is flourishing again, thanks to an edgy, off-Broadway play, a guest spot on HBO's "Entourage," full houses for his reinvigorated stand-up act and "The Aristocrats."

In the Paul Provenza documentary, which opened Friday at the Squirrel Hill Theater, roughly 100 comedians analyze, deconstruct and deliver their own version of the world's dirtiest joke, a burlesque bit that ends with the same punch line: "The Aristocrats."

"It's not the feel-good movie of the year and it's not a woman's film, really. It's a guy's sense of humor, the 15-year-old boy behind the school yard kind of humor," Saget says by phone. "Bad, wrong, dirty, ugly, wrong, heeheehee; that's what it is."

His participation has drawn reactions from, "Oh my God, I just saw 'The Aristocrats.' That's the funniest thing I've ever seen in my whole life. You're great" to "Why'd you do that?"

It's the equivalent of a secret handshake among comedians who never, ever perform it in public. The joke is typically told late at night, in the back room of a club where a dozen comedians are squeezed around a table designed for four.

The bit begins innocently enough and then takes a whiplash turn into foul territory involving incest, bestiality, scatology and obscenity. It's about the telling, the timing, the taboos, the topping of the previous comic.

"The Aristocrats" is filled with famous faces, including Saget, George Carlin, Drew Carey, Don Rickles, Paul Reiser, the Smothers Brothers, Robin Williams and Sarah Silverman, who is one of the women who proves it isn't a woman's film but it can be a woman's joke.

Director Provenza, reached in the editing room where he was working on the DVD of the film, describes the movie this way: "We are hanging out with our friends, and our friends can get pretty raw, and they're doing a joke that calls upon them getting as raw as possible. If you're into that, you are going to have the time of your life.

"We always say, if there's any word that ever offended you ... you will probably hear it a thousand times. You may not want to come." In fact, he planned to fly to Florida to be with his 74-year-old mother "in the theater, so I can talk her down."

Provenza and pal Penn Jillette, the larger, louder half of Penn & Teller, spent four-plus years recording their friends telling the joke.

"We didn't shoot it like a real movie," Provenza says. "We never set up lights, we didn't do anything elaborate with sound, we never did makeup or anything like that, because every time something like that happens, it's another layer of artifice."

They even ducked into the men's room of an Improv to shoot Jon Ross. It was the only quiet spot, and the producers had to get release forms signed by the patrons who used the facilities while Ross spun the joke.

Much to the moviemakers' surprise, "The Aristocrats" was nominated for the grand jury prize at the 2005 Sundance Film Festival and now is opening around the country.

"There are a lot of movies out there for you, but there is room on the shelf for something that's free and liberating as well," Provenza says. "If you don't like dirty jokes, if you don't like rough language, I highly recommend the penguin movie because they dress really nicely."

The documentary is dedicated to Johnny Carson, who gave many of the featured comedians their start.

"He has a rich history with this joke. This joke was his favorite joke in the world," Provenza says, and the one that guest Buddy Hackett famously told during a commercial break. Hackett timed it so that he would utter the punch line a second before the program returned to air.

"Johnny can't gain his composure, Ed McMahon is doing his characteristic bull moose guffaw, the band -- the instruments are banging into one another -- the audience is in tears, and every time Johnny would try to gain his composure, he would look at Buddy and it would start all over again."

Jillette, who maintained an e-mail correspondence with the dean of late-night comedy, told Carson about the movie but never asked him to step out of retirement and participate.

"He was a huge champion of the idea and a big cheerleader for the movie, and this is where it gets heartbreaking," Provenza says. "We were supposed to bring it over to his house and screen it for him right after Sundance, and he died while we were at Sundance."

Still, don't expect "The Aristocrats" to turn up on cable's Comedy Central any time soon.

"I loved sort of feeling like the fly on the wall, in terms of being a part of something that you know is going on in the comedy community on a regular basis and has such history," says Lauren Corrao, the cable network's executive vice president of original programming and development.

She found moments hilarious, but she's not sure how the public would react. Asked if Comedy Central would bid on the rights, she said, "We couldn't. You would just have to cut so much of it and bleep so much of it. ... That doesn't mean we wouldn't change our minds in the future."

Saget, the one contributor whom everyone wants to interview, was captured on film upstairs at the Laugh Factory in Los Angeles and insisted on seeing the movie before signing a release form. "When I saw the finished product -- I watched it with my manager -- I said I think I should sign it, because it's a funny movie."

He appreciated its "compounded vulgarity," the segments with Carlin, Reiser and Gilbert Gottfried, who tells the joke at a Hugh Hefner roast in the wake of 9/11. "It had that Peter Finch in 'Network,' 'I'm mad as hell and I'm not going to take it anymore' quality."

Although TV viewers know Saget from "Full House" and "America's Funniest Home Videos," he admits to a raunchy reputation. "Around comics, I've always been known for, oh, that's not dirty, this is dirty."

Longtime stand-up comedian Jim Krenn, half of the morning team at WDVE-FM, never told the Aristocrats joke but is familiar with it. He says, "If you get guys who are naturally funny, they can pull it off, and guys who aren't, they really can't. It's kind of a revealing joke in that sense."

Krenn once opened for Saget here and recalls, "Bob Saget was known, in the comedy clubs in those days, as extremely funny but with dark humor. It was always an inside joke among comics, when he got 'Full House,' it was, like, wow, he's playing this all-American dad kind of thing. That was not Bob Saget. His comedic style is definitely more twisted, and he has an edgier side than he showed in 'Full House.' "

But Saget had young children, needed a job and can do a G-rated act -- as he did on a recent Disney cruise -- or an R-rated one.

"The thing that changed me the most as a person was the play I did in New York," Saget says. "That's the thing I loved the most. 'Entourage' was a day and a half and 'Aristocrats' was 40 minutes," edited to a fraction of that. "The Paul Weitz play, 'Privilege,' was the best thing I ever did."

He portrayed a father accused of insider trading and says, "You walk through the door and you've got to be 100 percent, not 50 percent. Your throttle's gotta be fully open. I had these great people to work with, these two kids playing my sons, and I had a nervous breakdown every show," as per the script.

"It made me more honest than I've ever been, certainly in my acting."

And that, ladies and gentlemen, is no joke.