The much-anticipated announcement, subject of so many speculative column inches in recent months, has scarcely been made when there is a shimmer of music, like angels sighing, and the lights go down. Suddenly there are explosions. Corks fly, sparkling wine ejaculates from a cluster of bottles. Bubbles spill into the air and fall on to the lithe, lively bodies of young dancers in gold lame leotards, with sheer stockings and glittering stilettos. The bubble girls smile, and sing: "Felicidad! Happiness! For everybody!"
As the orchestra scurries along, strings driven by stabs from the brass section, it sounds so much like the old Pearl & Dean music that you can almost smell the hot dogs. The fiesta of kitsch on screen is so extravagantly over the top that I find myself laughing, and look around in embarrassment, mixed with wonder. Everyone else - from the press to the assorted celebrities, PRs and hangers-on - is rapturous, the sequins reflected in their eyes. Surely this isn't serious? The expression on the face of the man from Freixenet who introduced the film suggests it is. Deadly serious.
The music slows and swells, as the heavyweight figure of Senora Caballe fills the picture, full of gravitas with her arms wide open to envelop the world. "Happiness, dreams all true. Let your imagination fly. Everything changes. Life is hopeful, and the sun will always shine..."
Admirable sentiments. But despite their high-mindedness and the intense media interest, this is not the launch of a new political movement. It is the unveiling of a television advertisement for a fizzy drink. Freixenet is sparkling white wine, or cava. You may have drunk some on holiday in Spain, where the black bottles of Cordon Negro cost around pounds 3 a time. Or even in Britain where it is increasingly seen as a cheaper but highly drinkable alternative to Champagne. Freixenet (pronounced "freshernet") leads the world market in cava. But the most interesting thing about Freixenet is not the wine but the annual Christmas television ad.
It's the biggest thing on television, with a reputation for securing the services of some spectacularly big guest stars. Last year, 95 per cent of the Spanish population saw it. Not even the Queen gets ratings like that in Britain any more, and no performers have come close since Morecambe and Wise. For some idea of what the Freixenet ad is like, in both style and impact, remember Angela Rippon high-stepping down the staircase with Eric and Ernie and imagine they had spent millions on a lavish production, aired it like a party political broadcast, and asked the Fast Show team to direct. For all its pretensions - and there are many - the Freixenet ad bears unmistakable similarities to the cheesy Latino TV created by Paul Whitehouse and Charlie Higson. Maybe it's culture shock, or just plain ignorance, but at the launch I can't help thinking of their dodgy variety show, full of girls in glitter and paunchy, lecherous singers with unfortunate hair performing untranslatable lyrics. They come to mind as a Freixenet representative whispers translations in my ear, and the folk-pop group Ketama romp through their flamenco-tinged segment of the ad: "We live in a time of love, fashion, games and power, but I keep going with the same T-shirt..."
I look at him. Really? "Si. Really. The same shirt." Scorchio! Boutros Boutros-Ghali!
The advertisement previewed in Bilbao was shown to the general public for the first time on Thursday. The six-minute film was listed in all the newspapers alongside conventional programmes, and shown simultaneously on every television channel, just after the news at 10pm (prime time in Spain, where families eat their evening meal together much later than we do).
The man who introduced the advertisement from the podium was Pedro Bonet Ferrer, a member of the family that founded Freixenet near Barcelona at the turn of the century. Earlier on the day of the launch, as we drank cava at a tapas bar in old Bilbao, he had told me that 130 million bottles are produced every year, and just under half of them are drunk in Spain. "The spot is always a toast to the Spanish people, an approach to our friends, clients, customers - to the whole family of Freixenet drinkers." Speaking English rather than through a translator, Sr Bonet raised his glass. "We say, 'We hope things go better! Big wishes!'"
For 20 years giving such a toast meant buying in the biggest American stars Freixenet could afford. Liza Minnelli was the first to perform in the Christmas advertisement, singing the theme song from her hit film Cabaret in 1977. An ageing Gene Kelly reprised "Singing in the Rain" in 1982, twirling his umbrella and clicking his heels as golden cava bubbles fell from the sky. Shirley McLaine was followed by Raquel Welch, who sang "I'm So Excited" in a see-through top that encouraged Spanish men to share her enthusiasm. Victoria Principal sang "Fever" at a time when the television series Dallas was top of the ratings all over the world. Paul Newman and Christopher Reeve provided rare entertainment for the ladies, before Sharon Stone - star of "Instinto Basico" - teamed up with an emerging talent called Antonio Banderas for a mini-drama filmed on the Queen Mary liner. Kim Basinger sang "As Time Goes By" before Andie MacDowell recreated Beauty & the Beast in Gaudi's Parque Guell in Barcelona. The launches took place in Los Angeles, New York, London, and wherever else the stars happened to be, with the entire press entourage flown out at the company's expense.
Meg Ryan starred in 1997, but last year the ad was devoted to stars largely unknown outside Spain. There was great speculation that the Millennium Freixenet star would be Leonardo Di Caprio, and Internet rumours about Julia Roberts - but the company's research had shown that Spanish people would rather watch their fellow countrymen and women, at a time of growing regional and national identity. "It is good for our national pride to have more Spanish people in the spotlight, rather than import Americans," says Rosa Sanmartin, a daytime television presenter, as she enjoys the hospitality at the Guggenheim. The broadcast also fulfils a function in Spain similar to that of the switching on of the Oxford Street lights or the first pantomime performance. "For us, Christmas begins when the Freixenet ad is seen on TV."
The grand idea this year is that Monserrat Caballe should usher in a new generation of stars. So the piper Carlos Nunez makes love to the camera as he squeezes his airbag, long hair flying from a bald head that does not seem to diminish his sexual confidence. Tamara Roja, principal dancer with the English National Ballet, succumbs to stardust pulled down from the moon for her by a fresh-faced male member of the American Ballet Theatre. Miss Spain makes a shaky singing debut, and a soap star dresses as El Nino, the boy in the Freixenet logo. As the advertisement ends, they all raise a glass, in soft focus. Jose from Freixenet is still translating in my ear. "Life is hopeful, and the sun will always shine," the stars croon in the manner of Band Aid (although there is no suggestion that the proceeds will go to charity). "Happiness is feeling close, your friendship. Sing for peace, loosen your voice. Time to remember this is your moment. Do not forget it. Live and feel. Now is for always. Live and feel now the happiness."
Juan Bricolle, visual communications manager for Freixenet, insists that the stars and extras alike see it as an honour to be asked to appear in these advertisements (which, in this year's case, took 150 people to make). "It means you have made it. That's why every young girl wants to be a bubble girl when she grows up. They are spicy. They are beautiful, glamorous. Whenever there is carnival, in February, the young girls dress up as the burbujas they see every Christmas."
Despite this enthusiasm, none of the anonymous dancers who appear in the advertisement as bubble girls are present in the Guggenheim as we enjoy unlimited fine wine and food. Instead, they are represented by a row of faceless mannequins frozen in step. It would not be appropriate to have bubble girls present, says Jose, my guide and minder, because they are not meant to be individual.
"If a bubble girl came here people would see that she was a person - but she must not be a personality, just a bubble girl." Later, he tells me a joke. "This one man says to another, 'I have given more freedom to my woman.' The other fellow says, 'Oh yes, how is that?' The answer is, 'I have made the kitchen larger.'"
If the launch were in Britain there would be bubble girls everywhere, flaunting their sexuality; but Freixenet has its mind on higher things. Jose Ferrer Sala, the white-haired godfather of the company and son of the founder, outlines the approach he favours: "The stars must realise that they are not just working in an ad, but in a little piece of art."
Perhaps this is the cava talking, but it makes a kind of sense in the Guggenheim, where the main attraction is "The Art of the Motorcycle", an exhibition of gleaming vehicles. Upstairs there are galleries devoted to Andy Warhol, including his stack of outsized soap powder boxes. The Cuban artist Felix Gonzalez-Torres has piled sweets in silver wrappers in the corner of a curved room and called it Untitled (Public Opinion). A sign on the wall says, "Por favor, sirvase solo uno. Please take only one." The guide-book tells us that the missile-shaped liquorice candies question the validity of public opinion particularly in connection with militarism and patriotism in the US.
The unquestioning cameras are still following Monserrat Caballe as she cuts a huge Freixenet cake in the early hours, but once the stars go home the party breaks up quickly. Bubbles are still being projected on to the wall at 2am, but the band is playing loud disco music to nobody in particular. There are no obvious drunks. The people who came to celebrate this fizzy wine were too famous to fall over, or too serious. Outside, an illuminated staircase disappears into the titanium curves of the museum, and flaming torches on the terrace are reflected in the river. Cold mist sobers the partygoers as we climb aboard the coaches supplied by Freixenet, and all we have to keep us warm is the cheesy, sparkling memory of the ad. Scorchio!