The security guard for the posh Ruby Hill development in Pleasanton is giving the Flamingess a hard time. It's 2 o'clock in the morning — why is she trying to get past the gate with a van full of pink lawn flamingos and other plastic critters? The Flamingess and her wheelman, husband Armand Sutton, exchange looks. The problem with telling the truth is that it sounds like an elaborate lie.

In fact, they are here on business. For the past ten years, customers have paid the Flamingess to stealthily plant flamingos and other beasties in people's yards in commemoration of birthdays, anniversaries, and other important life moments. She moves only under cover of night, because her work is, as she puts it, essentially the adult version of toiletpapering. Tonight she's working at the behest of a high school Romeo who has decided dozens of carefully arranged lawn ornaments are the best way to invite a girl to the prom.

The guard, unimpressed, says he'll have to call the girl's house for permission.

No, no, Sutton protests. It has to be a secret. His tone is calm, but you can tell he's dying to lean out the window and gesticulate wildly at the side of the van, which proclaims the business' name: "Flamingo Surprise." The value of the Flamingess' service lies in the shock — which, admittedly, she is never around to see. By the time the sun rises and their victims stumble out of their houses and into their radically redecorated yards, the flamingo surprisers are back at home napping.

The exasperated guard gets on the phone with his supervisor and eventually sends the van to another gate, where a guard who is much hipper to the concept of late-night professional pranking happily ushers them through. "My lips are sealed!" yells Security Guy #2 as the van drives off.

Sutton navigates among the darkened McMansions and is pleased when the girl's house turns out to be a perfect target — a corner lot (fewer nosy neighbors) with a broad sloping lawn that will show off their handiwork to great effect. More importantly, the houses on the street look as if they all have sound-resistant double-paned windows, and there isn't a light on anywhere.

Sutton kills the engine and the two slowly open the van's doors and creep around to unload supplies. Instead of the traditional flamingos, tonight's client has opted for something more romantic. So while the Flamingess sets up a big white marquee board with the prom invite, Sutton stabs dozens of giant smiley faces and red plastic hearts into the grass.

The deed done, the Flamingess snaps a photo for a blog she keeps of her adventures (FlamingoSurprise-CA.blogspot.com) and she and her hubby try not to titter as they behold their work. Quite frankly, it is awesome. Or at least, it is the sort of awesome John Waters would appreciate. As the Flamingess puts it: "Two is tacky. Fifty is art." They beam at each other conspiratorially as they hotfoot it back to the van and peel off toward the next job.

They do this all night, every night, regardless of pounding rain or national holidays.

• • • •

A decade ago, the Flamingess was a bored corporate drone named Kerry Hargraves, who during her morning commute happened to hear someone on the radio mention flamingo-flock rental. "It just stuck in my head; that is just so bizarre," she recalls thinking. "I have got to find more out about this!" Flamingo rental, or as it is more technically known, "lawn greeting services," turned out to be a fledgling industry. In 1996, Hargraves tracked down the brothers who operated the original Flamingo Surprise outfits in the Midwest, and basically pestered them until they agreed to teach her the business and let her license the name.

So Hargraves adopted the Flamingess moniker, and began to phase out her corporate work in favor of flamingo-ing people's houses. The business soon outgrew the garage of the couple's Alameda home, so they moved it to the Oakland warehouse they now live above. Their critter repertoire expanded rapidly to include penguins, dinosaurs, teddy bears, buzzards, bats, cows and frogs, all of which lend themselves to punny marquee messages like "Hoppy Mother's Day" and "Look Who's Moooving In!"

Sutton, a retired auto mechanic, eventually joined his wife's company, and last October Hargraves finally made stealth flamingo deployment her full-time gig. Flamingo Surprise delivers anywhere within a hundred-mile radius, and charges by distance — prices range from $85 to $250. That'll buy you a flock of fifty flamingos, or thirty of the other animals.

When Hargraves started out, she was one of the first lawn-greeting services in the United States. Now, she estimates, there are more than one hundred. They have their own business association, as well as splinter groups like the "storkies," which specialize in gigantic stork-shaped baby announcements. She has commemorated countless birthdays, graduations, retirements and holidays, plus two marriage proposals, one funeral, a surprising number of divorces, and several jobs that were clearly revenge for previous flamingo-ings. Victims often call begging to know who ordered the hit, but Hargraves claims "flamingo-client privilege."

Here are the other rules of flamingo-ing: No giggling. No flashlights (too visible). No point in wearing rain gear ("Everything's waterproof, even us," Sutton points out) or dark clothing ("If you don't get caught, it doesn't matter what you're wearing. And you don't want to look like a burglar," Hargraves notes.) You leave a brochure on the door explaining what the heck's going on and saying you'll be back the following night to spirit the flamingos away. "We trash the place, and then we come clean it up again," Sutton promises.

There are obvious hazards to avoid, including watchdogs, dog poop, automatic sprinklers, people with dangerously dark or steep yards, people who sleep with the windows open, suspicious neighborhood watch captains who note down license plate numbers, and grouchy real-estate agents and homeowners' association types who gripe that having a few pink plastic flamingos in the neighborhood for 24 hours will bring down property values. Flamingo Surprise has gotten busted maybe ten times in a decade of jobs, mostly by victims who were awake and heard them drive up. The cops were called on them once. Sutton just gave the officer a brochure and went back to work.

For the most part, pretty much everyone the Flamingess crosses paths with is having a good time. People who call her to punk a friend are in a punchy mood, Hargraves says, "because they're up to something." Most victims enjoy being neighborhood mini-sensations; plenty call to say thanks, or describe the parade of cars circling their block or honking in salute, or all the people running over to take pictures. As for Hargraves and her hubby, they love sneaking around town after midnight, executing goofy acts of goodwill, being secret agents in a vast lawn-based conspiracy. "Every time you make a setup," Sutton says, "when you leave you feel like you got away with something."

Nevertheless, there's always the risk they won't get away this time, so the duo is a bit apprehensive as they pull up to the next victim's home in Alameda — the houses are older and less soundproof here, and they'd been warned that this one has a dog. But as Hargraves and Sutton tiptoe through the grass, arranging the flamingos around a signboard proclaiming "Happy Flocking 50th Birthday!" both the pooch and the neighborhood stay soundly asleep. Within a few minutes they are back in the car, mission accomplished, rolling homeward.

As they check back into their apartment at 3:30 a.m., they're ready to unwind or perhaps sleep a bit before they begin taking the next day's orders. The Flamingess and her wheelman settle into their recliners, put their feet up on the coffee table, and drink some red wine. They seem pretty flocking happy indeed.