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Character Snow White during live performance of Steve Silver's Beach Blanket Babylon, celebrating its 40th anniversary at Club Fugazi in San Francisco, Calif., on Wednesday, May 28, 2014. (Josie Lepe/Bay Area News Group)

Hats off to Beach Blanket Babylon!

Steve Silver's unstoppable headdress homage marks its 40th anniversary this month. The longest running musical revue in the nation, if not the world, it has played to an estimated 6 million people, logging more than 15,000 performances. A beloved San Francisco institution that's as much a trademark of the city as the Golden Gate Bridge, Coit Tower and cable cars, this slap-happy revue will be honored at a public ceremony at noon Friday at San Francisco's City Hall.

There is also a gallery of humongous hats -- a trademark of the show -- on display at venues throughout the Bay Area, from Berkeley Repertory Theatre and American Conservatory Theater to Davies Symphony Hall (details at www.beachblanketbabylon.com). Oh, and did we mention that venerable San Francisco ice cream maker Humphry Slocombe has even debuted a new ice cream flavor in honor of the occasion? If you can't make it to one of the formal festivities, take a lick of Beach Blanket Babylon Goes Bananas.

"It's one of the earliest theatrical experiences I can remember, and its wit and theatricality were not lost on me even at that age, " says Cal Shakes artistic director Jonathan Moscone, who has been a fan of the show since his parents threw his 11th birthday party there. "Some people may mistake Beach Blanket Babylon as a tourist show, but it's a local favorite -- I've seen it over 20 times and have loved every time, finding new moments and constant vitality in the work."

When Steve Silver first launched his chapeau extravaganza in 1974, in the back room of the Savoy Tivoli restaurant in North Beach, the impresario charged a handsome $2.50 for a 45-minute spoof of creaky old beach flicks. He figured the loony lampoon would be popular enough to run six whole weeks.

Forty years later, the now 90-minute mashup of massive millinery is bigger than ever. His eccentric creation -- crammed with pop culture guest characters, ripped-from-the-headlines jokes, silly song-and-dance routines and puns and double entendres galore -- is still packing houses, playing eight shows a week at the Club Fugazi in North Beach. Silver, who died of AIDS at the age of 51 in 1995, created an ahead-of-its-time cabaret that lives on and on.

"Steve would be so proud to see that the show is still thriving, still going strong all these years later," says his widow, Jo Schuman Silver, who has produced the show since his passing. "It's his vision and his legacy, and we are just the keepers of the flame."

Indeed, fans of the show credit the redoubtable Jo Schuman Silver with keeping the farce torch lit through the years.

"A huge part of the lasting appeal of 'Beach Blanket' is the incredible heart, generosity and wit of Jo Schuman Silver," says Carey Perloff, artistic director of San Francisco's American Conservatory Theater. "I never had the pleasure of knowing Steve Silver, but Jo has clearly taken his torch and run with it, in all the best possible ways. She has made sure that the show is topical and hilarious without being too trendy or literal, that it has hope and joy while still managing to laugh at itself, and that it is always impeccably produced."

For the record, Silver honed his punchy performance style while a student at San Jose State, where he became famous for raucous event planning, particularly fraternity blowouts for the Theta Chi house.

"His frat brothers are still huge fans of the show, and it's wonderful to see them in the house," says Silver.

After graduation, Silver's affinity for farce led him to take up busking on the streets of San Francisco, which is how he landed that fateful gig at the Savoy. The rest is kitsch history.

"His spirit is definitely still with the show," says Silver. "He's in the theater every night."

The slapstick is constantly evolving in the show's loopy pantheon of hats and gags. The pop culture pastiche combines "Saturday Night Live"-style skits with local in-jokes and groan-worthy puns. Over the decades, the show has thumbed its nose at everyone from Miley Cyrus and Martha Stewart to Katniss Everdeen and Queen Elizabeth (who has also visited the show).

"We try to stay clean, and we are never mean-spirited," says Silver of the show's humor. "We laugh with the people we parody and not at them."

World leaders and one-hit wonders rub elbows in a symphony of silliness that includes everyone from the Obamas and Oprah Winfrey to Honey Boo Boo and Justin Bieber. In the old days, Silver tried hard to appeal to all age groups because the cutting edge wisecracks didn't land with kids or senior citizens.

"Now everyone is on the Internet," she says, " and everyone gets all of the pop culture jokes."

Silver says the secret to the show's insane success lies in its over-the-topical spoofs. Change is part of the show's DNA.

"If something big happens in the news, we put it in that night. I am not kidding," says Silver. "We are that fast."

Indeed, the wigmakers and costume seamstresses even pulled an all-nighter after the much-ballyhooed royal wedding of Kate Middleton and Prince William at Westminster Abbey.

"We were up all night, but we pulled it off," says Silver. "And it paid off, because the audience roared."

Of course, some characters have the power to endure, such as the pantsuit diva Hillary Clinton.

"The Clintons are the gift that keeps on giving," says Silver. "They never get old."

Songstress Renee Lubin plays a dozen parts, including an elegant Michelle Obama, a glittering Glinda the Good Witch, a chap-sporting country western gal and a wiggy Tina Turner.

"It's truly an honor to be a part of a show like this,'' says Lubin, who has been with the show for 27 years. "There is nothing out there quite like it. There is no feeling like putting a smile on someone's face. You can't beat it."

Of course, not all of their parodies hit pay dirt. If a skit bombs, Silver is ruthless about cutting it.

"I watch the audience and if they're asleep, it's out," says Silver. "They are the judges, not me."

To be sure, even the most jaded theatergoer will gawk at such beauties as the 15-foot-tall Silver San Francisco Skyline Hat, which is said to hold the record of largest hat ever worn on stage. The show's commitment to topping itself is why "Blanket's" brand of camp never gets musty.

"Every time I go, I discover something that feels fresh, inventive, alive, and newly minted," says Perloff. "And it's so inclusive. Whether you're a native or a tourist or something in between, BBB makes you proud to be in San Francisco. I adore them."

The glitzy gag machine also benefits from its synergy with San Francisco culture, it's embrace of the city's ethos.

"It's iconic, like sourdough and Dungeness crab, but for the arts," says Lisa Mallette, longtime fan and native San Franciscan, "and it has always been a sense of pride that we have such a fabulous, outrageous, innovative piece of long-lasting, relevant theater."

That's why no tourist wants to go home without having seen it.

"The show is very much like the city," says Silver, "It's funny, crazy, quirky, beautiful and anything goes."

Silver is also certain that "Babylon" will never have to hang up its hat.

"Honey as far as I am concerned, the show will run forever," says Silver. "I plan to do this until I drop. It's that much fun."

Contact Karen D'Souza at 408-271-3772. Read her at www.mercurynews.com/karen-dsouza, and follow her at Twitter.com/karendsouza4.

'BEACH BLANKET BABYLON'
When: 8 p.m. Wednesdays through Fridays, 6:30 and 9:30 p.m. Saturdays, 2 and 5 p.m. Sundays
Where: Club Fugazi, 678 Beach Blanket
Babylon Boulevard, San Francisco
Running time: 90 minutes, no intermission
Tickets:$25-$130, 415-421-4222, www.beachblanketbabylon.com
Online: Scan this code with your smartphone or go to www.mercurynews.com/entertainment to see a slideshow from "Beach Blanket Babylon's" 40th anniversary show.

ABOUT THOSE HATS
Some facts and figures about the dozens of hats "Beach Blanket Babylon" utilizes.
Oldest: The "Pineapple Princess Hat," above, debuted in "BBB's" first production in 1974, worn by one of the show's first stars, Nancy Bleiweissa, in a nod to Carmen Miranda. It remains part of the show today.
Newest: The show recently added a hat spoofing pop singer Pharrell's Smokey Bear hat, which became a global sensation earlier this year.
Largest: The San Francisco Skyline hat, which debuted in 1999, measures 15 feet wide, 15 feet tall and 4 feet deep.