CERGY-PONTOISE, FRANCE -- "Everyone knows Mickey Mouse," Guy de Boisgrollier said. Outside his office, loudspeakers blared ceaselessly into the rains that have been the French spring and summer.

"And all the people and the government were busy talking about whether it was okay for Disney to come into France -- whether there was too much Americanism in Disney.

"So, in one way it was very good for us because they were talking theme park," said Boisgrollier, 39, director general of France's first (and only) theme park, the three-month-old Mirapolis. "While they were talking, we were doing! This," he declared, "is how the French build a theme park!"

Snapshot: Where once Monet painted lilies now sits an odd collection of high-power lines, Euro-tech and bright shapes, looking for all the world like something dreamed up by Picasso under the influence of LSD.

In fact, said Boisgrollier, Mirapolis is something of "a laboratory experiment"; a most unlikely one involving more than 500 million francs ($85 million); a cartel of Saudi, Dutch, Indian, Japanese and Moroccan interests, French banks and that symbol of pop fantasy, Club Med, with some corporate sponsorships from Nestle, Fuji film and Coca-Cola tossed in for good measure.

If successful, it will generate waves far beyond its cornfield location in a valley 30 miles northeast of Paris, historically known as an artists' retreat. Successful or not, the half-readied catchall park is shaping the future of a billion-dollar theme park industry that has grown overnight like a giant plastic beanstalk in the land of fresh haricots verts.

"It's a new kind of leisure for the French," Boisgrollier contends. "We have to let people know that once they get inside (admission is $17 for adults, $12 for children) everything is free. It's very hard to make French people understand that they don't have to go to their pockets every five minutes."

What Boisgrollier describes as "a crazy dream," conceived in 1980 by architect Anne Fourcade, moved onto the drawing board in earnest in 1984 with the entrance of Saudi banker Gaith R. Pharaon and the corporation's subsequent acquisition of 162 acres.

"We built it in 14 months, too fast," Boisgrollier said. "No time to think ... only to do. We had to be first because there were several parks being talked about and we believed the banks and investors would wait for the results of the first park's first season."

Even after construction began, plans were still on the drawing board. "We studied American parks," the former Nestle sales manager said. "First, we decided that the French would behave like Americans, so we decided on fast food in the park.

"Well," he now admits, "it doesn't work that way."

There have been myriad changes since Opening Day, last May 21. Primarily, the French don't want fast-food superdog and nacho-wave fare. Instead, they want splendid, leisurely 90-minute lunches. Park stays average, management says, "four hours 'plus the lunch' because in this country, we always say 'plus the lunch.' "

Secondly, "we thought they were proud of our culture," another park official said sheepishly, "so the attractions came from our legends. Now, we find people don't care so much about culture."

According to surveys of departing patrons, what they want is more "mane`ge d'e'motion," (shake-'em-up rides) than the park currently offers -- "something with curves to it," Boisgrollier said. They will apparently get it as part of a $90 million expansion during the next five years that will also include a haunted mansion and "a future world, like Disney." Snapshot: Louis XIV, "The Sun King," in silk raiment, powdered wig and shades leads the 3 p.m. parade around the Courtyard of the Snackbars on a lawn tractor.

The key phrase is "like Disney."

It issues off everyone's lips with an awed mix of curiosity and reverence, entering each conversation as though a mouse-eared shadow larger than the Eiffel Tower looms just over the horizon. Sooner or later, every Mirapolitan introduces the phrase.

"We are very anxious to see Disney in Paris. I just hope they don't have the weather we've had," Boisgrollier says, lighting another in an endless stream of cigarettes. Like its counterparts in Los Angeles and Orlando, he believes, Euro Disneyland's estimated 10 million annual attendance will spill over into neighboring attractions. "We don't have the capacity with our park to do 25 percent of the people that Disney can do. We can make money if we accept the difference. There's room for three, maybe four, parks around Paris."

His investor group is not the only one bankrolling this belief. Before Euro Disneyland's Magic Kingdom opens west of Paris in 1992, two more major theme park operations will already have opened their gates.

In August, contracts were signed for a theme park celebrating the French cartoon warrior Asterix. Construction is expected to begin in September across the Valley d'Oise from Mirapolis, threatening to turn this peaceful countryside into France's "Lost Valley of the Theme Parks."

Later next month, groundbreaking is scheduled in the Moselle district, 180 kilometers east of Paris, for an ideophonic tribute to the Belgian cartoon characters Les Schtroumpfs (known in English as the Smurfs). In large measure, the success and substantial investments of Asterix Park, "Smurf City" and even Disney's own Europerations are keyed to Mirapolis' public acceptance.

Marc Tombez is the keeper of Club Med's secrets, its top executive in charge of personnel training, an expert in "communication and service formulas" and, since April, Mirapolis' adjunct director general. Tombez is responsible for "Miralliance," Club Med's 300-hour training program for 600 park employes. It is Club Med's first such program outside its own 120 resorts.

"This park is a very special experiment," he says. "Nobody in France -- nobody -- has worked in this kind of industry. In the States, you have Disney as a reference for this kind of 'people technology' -- and you have a culture of service and courtesy.

"The tradition of courtesy in France," he says, with despairing understatement, "is different."

The link with Club Med developed, Tombez says, because Mirapolis principal Pharaon is also the single largest private partner in Club Med, which in turn owns 4 percent of the theme park. Through Pharaon's intervention, Club Med President Gilbert Trigano has made Mirapolis a pilot project in a companywide diversification plan.

(Last month, Club Med reportedly assumed overall management of Wonder World, a glass-enclosed, high-tech multitheme park planned 70 miles north of London. The first of its 13 interconnected parks is expected to begin receiving 6 million visitors a year in 1990.)

Tombez sees Club Med's future in park hospitality growing, including involvement with "the biggest," as he calls it. "The biggest cannot transfer its culture directly to France. I think we'll work together because they know their strengths and their weaknesses."

"The reaction from the public and the press," Boisgrollier says, "has been very good to us, except those who compare us to Disney. There is nothing here to compare to Disney. It is as if someone wants to compare a truck to a bicycle -- both go on the road, but for different purposes. So we've tried to do something different!"

Snapshot: Gargantua, a 110-foot-tall Rabelaisian giant, strides the land, a life-size cow impaled on his fork. His hollow body houses a fanciful alimentary canal tour before peristaltically delivering visitors a panoramic view from his neck. He is, one official boasts, "the biggest empty-headed statue you can go to in the world."

The "something different!" is exactly that -- spiraling architecture and "diorama" rides predominate the landscaped grounds, all loosely celebrating French legends and cultural themes (excusing Hansel and Gretel's presence under French pseudonyms in the Broccoli Forest's Palace of Madame Stale Bread).

Rushed open by 120 design, engineering, architectural and construction firms over 14 months, the half-finished park's attractions range from banal "kiddie rides" to several breathtakingly surreal showcases and abstract pavilions. For example, an ancient Brittany legend of rubber monsters inexplicably dissolves into a fantastically choreographed "designer" laser show of Kubrickian concept in one as-yet-unfinished funhouse pavilion. Its bright neon rings, though beautiful, are a bit heavy on the symbolism for the average 8-year-old.

In other areas, single rides operate on large tracts (destined to contain dozens of rides) encircled by wide vacant concrete walks that bridge distances between attractions. Maniacally "happy" music pounds unendingly from loudspeakers.

The effect is Ray Bradbury mixed with some nice Fellini touches.

Yet, there are tremendous successes. Arched skywalks lead to an 800-seat Theatre of Marvels designed by Seban (chief architect of Mitterrand's new Bastille Opera House) and featuring illusionists and performers from the Lido and Moulin Rouge. A 1,000-seat striped circus tent houses a resident clown troupe's traditional French character performances. Other typically French distractions are a boxwood maze, marionettes, carousels and toy boat sailing.

There is also a good smattering of what's best described as tinkertoy versions of American Midwest state fairism. In multimedieval theater, a Leonardo da Vinci robot (his arms and legs not yet fully operable) flails away at the Mona Lisa. Officials say technology was not readily accessible for most of the attractions, so research and development costs added to the price of attractions like Fourcade's giant. Gargantua's head alone cost more than $1 million ("and there's nothing in the head. It's completely empty," park spokeswoman Caroline de La Jarrige remarks). This head, incidentally, is the centerpiece of a $3 million advertising campaign, including more than 17,000 posters plastered across Paris' Metro system.

Snapshot: Dozens of French tricolors slap into a stiff tattooing rain. Beneath umbrellas a handful of patrons caught in the sudden gray afternoon shower, rush away from turnstiles.

Passing a giant pink grasshopper, one family stops, posing for pictures before hopping on a waiting bus. In the background, a mournful Dixieland clarinet solos farewell beneath a dripping tent.

"This is our war," Boisgrollier says, acknowledging that because of weather attendance has not met predictions. Or investors' expectations. "This is our 52nd day of rain ... we've had only 14 days with sun ... we had a big opening day but it was very cold ... there's been more rainfall this year than in 1972 or in 1945 after the war.

"It's impossible to conceive of this weather. And still people come ... Yesterday, a Sunday, it rained all day long and still 7,000 people came instead of the 25,000 we expect."

Initially officials hoped for 1.8 million by October. At this point, they anticipate 1.4 million will actually pass the Green Elephant entrances. By August, a half million had visited, 200,000 fewer than projected. "Forget trying to explain it," he says, loping over a puddle. "When you have investors in Saudi Arabia where they pray for God to bring them rain and then you try to tell them over the telephone that you don't want God to send any more rain here. That, instead, you actually WANT the sun. Forget it," he laughs. "They think you're peculiar!"

Meanwhile, there has been little word on Euro Disneyland. Officials restate only what has already been issued in the (French-only) press kits concerning the 4,800 acre Marne-la-Valle'e site.

The Magic Kingdom is scheduled to open in 1992, adjacent to the TVG and Metro RER rail lines stretching the 28 kilometers to Paris. As of now, specific details concerning park attractions, the potential second theme park (like Florida's Epcot) for the site and facilities are unavailable. Recruiting is underway in the United States for engineering and construction personnel.

Disney personnel in France, who moved onsite in early August, would confirm only that current plans indicate that the park, which is to operate year-round, "will be covered on a much larger scale than Tokyo Disneyland," to shield it from the weather.

"I'm sorry I can't give you much information," one official explained, "Company policy is not to release much information because they don't want the public to get oversaturated with stories. Try back in three years' time.