If so, they should be warned that this will be a close encounter of the propaganda kind. The UFO is a mere replica. There will be no Martians on board, just the more down-to-earth message that a food company is launching a new product. The brand, it hopes, will stand out by being viewed as off the wall, original and fresh - just like the stunt used to promote it.
This is advertising, Jim - but not as we know it.
While the promotion may be ground-breaking, the British public has already had plenty of exposure to bizarre stunts. In the summer of 1998 Channel 5 acquired the rights to make a new series of Lassie, TV's Fifties canine heroine.
Despite Lassie's stirring deeds and ability to communicate long-winded warnings just by barking, an image makeover was now needed for the more showbiz-conscious Nineties. So after a Lassie lookalike had been selected (a male, as it happened), he was filmed stepping from a corporate jet wearing a pair of shades. From the airport, he checked in at the Waldorf, shopped at Harrods and then made a celebrity visit to Battersea Dogs' Home.
Both these promotions were dreamed up by the quaintly titled Cunning Stunts, whose name sums up its campaigns: make them attention-grabbing and memorable, and then get the media in to film them. Cunning Stunts has been going for just over a year but its managing director, Anna Carloss, says the demand for its services reflects a "gap in the market".
The niche, she explains, is building awareness of a brand in a congested market where thousands of products are screaming for consumers' attention. The solution is to shout even louder, while saying something different.
The company's most celebrated stunt was carried out in May when it was hired by the men's magazine FHM to publicise an annual readers' poll for the world's 100 sexiest women. Ms Carloss says that because the media can't always be relied on to turn up, it is important that promotions can be viewed as coherent advertisements in their own right. So Cunning Stunts' decided to take one of the girls featured in an FHM photo-shoot and marry the picture with the idea of voting. The result: a nude image of the TV presenter Gail Porter projected at night across the Houses of Parliament.
Such risque promotions may seem like a product of the Nineties but, as a new Radio 4 series called Stunts explains, they have been around most of the century. Even in the Fifties, for example, Guinness was pushing at the boundaries of mainstream advertising while wondering how to build a global identity.
Its solution was to drop 200,000 bottles of Guinness Export into the Atlantic, Pacific and Indian oceans and hope that beachcombers around the world would find them and spread the word.
Unfortunately, this bold initiative backfired. Worried that dumping bottles at sea might offend the environmental lobby, Guinness claimed it was simply an exercise in making sure the seals were watertight.
Pepsi-Cola also found itself dogged by controversy when it launched the biggest-ever commercial publicity stunt to publicise its change in colour to electric blue. In April 1996, at the start of a three-year promotional campaign, costing around pounds 330m, Pepsi paid The Mirror to print on blue paper, arranged for an Air France Concorde to be painted blue, and got the cosmonauts on board Russia's Mir space station to pose with a giant inflatable Pepsi can.
The space-age project soon got bogged down in more earthly rivalries. Perhaps motivated by Pepsi's choice of sponsorship, The Sun newspaper claimed the promotion had not boosted sales. Other papers reported - wrongly, according to Pepsi - that the 300 litres of blue paint applied to the Concorde had stopped it from going supersonic. Meanwhile, as Mir orbited the earth, Nasa's Endeavour space shuttle blasted off carrying an experimental drinks dispenser - stocked with Coca-Cola.
A spokesman for Pepsi says the stunts have proved a huge success, and that its share of the UK cola market has risen from 15 per cent at the relaunch to 20.5 per cent today. But Pepsi's experiences do illustrate that the best-laid stunts can be compromised when other companies dilute the message.
For instance, while seeing itself as a space pioneer, Pepsi may not have been gratified to learn that no stunt is too ridiculous for the cash-strapped Russian Space Agency. That's why the hapless cosmonauts on Mir have also had to advertise Swiss watches, drink Israeli milk and wear German knickers.
None of this is to say that commercial publicity stunts need be a huge financial gamble. Ms Carloss says the promotions organised by Cunning Stunts have each cost under pounds 10,000 - a relatively small proportion of many corporate advertising budgets.
The problem is that there is no sure way of measuring their success. As Hamish Pringle, director of marketing strategy at the Institute of Practitioners in Advertising, says, they form a small part of wide-ranging ad campaigns and their contribution is hard to quantify except in the amount of column inches generated. In those terms, he believes, campaigns like French Connection's "fcuk" succeed purely by being controversial.
That said, there is a question mark over the shelf life of stunts because nothing dulls the element of surprise like too many surprises. Thirty years ago, soap and detergent companies put characters such as the Fairy Snowman on suburban front doors to tempt housewives with cash prizes. After a while the stunts reached saturation point and thus was born Square Deal Surf - "no gifts, no gimmicks, just 18 per cent more powder".
There is also the danger consumers will become confused. Last week, Heineken unveiled a promotion to cash in on the Rugby World Cup, which kicks off next month. Fronting the launch was Julia Carling, ex-wife of the former England rugby captain, who has swapped one beer brand for another by agreeing to call herself Julia Heineken for the duration of the tournament.
While doubtless relieved she hasn't been hired by Oranjeboom, Ms Carling is precluded by ITC rules from using the name Heineken on her TV video show. For the purposes of the programme, therefore, she will be known as Julia H. Confused? You might be.
`Stunts' is being transmitted on Radio 4 at 9.30am every Thursday until 30 September.