Gay divorce can be a tough sell in the Castro. Especially if you're advocating for it while dressed as an orangutan in a top hat and gold disco pants.

But because the guy you're with is wearing a bright blue shirt, bright red pants and a "Yes, Bush Can '04" name tag, few will doubt that you are trying to garner support for the president before the election.

At least that's what liberal activist-pranksters Andy Bichlbaum and Mike Bonanno found on a recent visit to San Francisco.

The orangutan suit is a leftover getup given to them by Sal, a friend who creates costumes in Hollywood. Bichlbaum and Bonanno put it to use in the Castro to show passers-by just how "unnatural" male-to-male marriages are, Bichlbaum says. Outrageous as the stunt was, he says, "Nobody got it. Nobody laughed."

The prank even included handing out an official-looking fact sheet from the Bush campaign. The flyer promoted a computer program that, once installed on home systems, could annul gay marriages over cyberspace.

"It's like this administration is so surreal, the things it does are so out of control, that nobody's shocked by anything Bush does," Bichlbaum says.

The gay divorce prank was just the latest in a series of satirical spectacles that Bonanno, 36, and Bichlbaum ("just a little older," he jokes) have pulled off in order to make the public think twice about the decisions made by people in power. Their antics and adventures are celebrated in "The Yes Men," a funny and enlightening new documentary that's named after them.

As Bonanno explains in the film, "We target people we see as criminals and we steal their identity to try to make them honest."

Before Bichlbaum and Bonanno began traveling the country "promoting" Bush -- other recent pranks have included circulating petitions calling for tax cuts for the wealthy and the reinstatement of the draft -- the clean-cut, witty pair posed as representatives of the World Trade Organization, the global body that regulates trade between nations. It's this earlier activism that's captured in "The Yes Men."

One might think of the WTO as a dry, arcane entity to choose to parody, but it's a powerful organization that the Yes Men manage to con with surprising ease, ridiculing its policies with brazen pranks -- and drawing worldwide media attention in the process. (A book, also titled "The Yes Men," has been published to coincide with the film's release.)

As with the ape suit in the Castro, the targets don't see through the pranks in "The Yes Men." The most patently absurd (and wickedly amusing) ruse in the film, directed by the makers of the equally uproarious documentary "American Movie," involves Bichlbaum addressing a business conference in Finland. Going by the improbable name of Hank Hardy Unruh, Bichlbaum delivers an earnest lecture in which he talks about the Civil War being "the bloodiest, least profitable war in the history of our country." He then goes on to theorize that slavery, today, could be a moneymaker. Astonishingly, there are no reactions from the audience of 150 people. They appear nonplussed when the prank gets crazier -- and involves a golden spandex suit and huge phallus.

When the Yes Men were formed, in the late 1990s, it was an ideal marriage of two men who share political views (informed by relatives having lived through the Holocaust), an appreciation of Dadaism and Surrealism, and a history of pranks. Bichlbaum, who lives in New York, had made something of a name for himself when, as a video game programmer, he replaced "bimbos," he says, with "boys in swimsuits kissing each other." Bonanno, who teaches at Rensselaer Polytechnic Institute in upstate New York, had created the Barbie Liberation Organization, covertly swapping the voice boxes of Talking Barbie and G.I. Joe dolls.

Together, Bichlbaum and Bonanno created www.gwbush.com, a spoof of then- presidential candidate George W. Bush's Web site. Bush did the Yes Men a favor when he publicly condemned "the garbage man" behind the site and said, "There ought to be limits to freedom."

Now, with another election nearing, the Yes Men are again focusing their attention on Bush. In August, they began a national "Yes, Bush Can!" tour with a donated bus they adorned with the president's image. The gas guzzler blew a gasket, but the Yes Men expect it to be on the road again soon, blasting "campaign" dance songs that make mention of Bush ... and booty. (The Yes Men's progress can be charted at their Web site, www.theyesmen.org.)

In Oregon, the Yes Men recently made some friends with their Smokey the Log mascot (Bichlbaum in yet another suit). Sure, Smokey the Bear is cute, but as their blog states, "Bears are simply not useful; logs are." Among those who have thought what the Yes Men are saying about the environment is swell is a congressional candidate and a former governor of Oregon.

No, the Yes Men haven't persuaded many people on the road to change their minds, to see the absurdity of what they're saying. But Bonanno says this "makes us want to keep pushing further, keep getting more hyperbolic and coming up with more sinister ideas."

Maybe they'll even try sincerity. "We've had the idea for a long time of going around saying that Bush is 'coming clean' and changing this or that policy," says Bichlbaum. "Like being born again -- again."

After the election, Bichlbaum says with a laugh, "We'll immediately turn the bus into an anti-Kerry bus if Kerry wins. Because there's not that much difference between them." But if Bush wins, he adds, "I'm completely dried up for ideas."