Thomas Sutcliffe: Cool plus cool just leaves me cold

It must have seemed like the perfect marriage. On the one hand, you had Apple's latest ad campaign, which personifies the long, sniping war between Mac and PC with two characters - one uptight and nerdy, the other handsome and relaxed. On the other hand, you have a British sitcom - Mitchell and Webb's Peep Show - which depends on the odd-couple partnership of an anally retentive worker bee and a laid back, hop-head grasshopper. So, the thinking must have run, why run a big casting call for a British version of the ads when you can just piggyback on an established franchise. The demographics look just right and these guys have good comic timing anyway. It's a double win surely?

Except that it isn't - once you've got past the novelty of watching the first couple of ads. There's nothing really wrong with the theory, which predicts that cool multiplied by cool should stomp all over the opposition, but, in practice, an odd kind of polarising effect takes place. Rather than amplifying each other, they cancel each other out - so that both parties turn out to have something to lose from the combination.

Obviously, Apple will have no problems associating its competitors with Mark, a flustered neurotic prone to panic attacks. But do they really want to identify their own product with a hedonistic, klutz-like Jeremy? The dynamics of Peep Show aren't geek versus hero, but a combat between two very different kinds of inadequacy... and if Jeremy were a computer, he would almost certainly be boasting about his unrivalled ability to surf porn websites. He would also be very difficult to wake from sleep - which, as it happens, is a problem Apple has been having with some of its newer laptops.

At the same time, Mitchell and Webb find themselves performing lines that are sadly underpowered compared with the excruciating embarrassments they contrived for their television series. There's nothing here to compare with the sequence in the sitcom where Mark discovers that his last strawberry yogurt has been used as a sexual lubricant by his flatmate. And while it's true that they probably get more money for the ads than they ever did for the original series - there's still a sense that the characters they created have been pulled out of true to meet the requirements of the marketers. A capsule version of Peep Show in which Jeremy's swaggering self-assurance turns out to be justified has rather missed the point of the original. As does an ad which fails to grasp the merits of Mark's exasperated, embattled traditionalism.

The ads have been greeted in some quarters as a classic instance of comic sellout - which seems a little naive, given the long and lucrative connection between comic talent and advertising. And it may also miss the point about exactly how kudos flows between celebrity and product these days. It used to be the case that only the star had anything to fear - their own glamour potentially tainted by association with the banal or the everyday. Certain products were usually exempt from this dread - thanks to their own association with leisure or glamour - but there was always the possibility of pollution, of talent brought low by contact with the domestic or the mercantile. And in almost every case the celebrity was assumed to be conferring some grace on the product - which was one of the reasons why the notion of selling out arose in the first place.

These days, things aren't quite that simple any more. For one thing our expectations of adverts are much higher than they used to be, so that it's far from inconceivable that a commercial break will deliver more wit and pleasure than the programme it interrupts. Ad campaigns can even take on a life of their own - as was recently demonstrated by the return of Johnny Vegas's double act with a knitted chimp. There weren't many complaints then about the debasement of a comic talent - only an appreciation of the invention with which the back story had been filled in - and admiration for the funny, self-referential way in which it acknowledged that fame can always be used to lever a hard sell, even the entirely fictitious fame of a stuffed woollen monkey.

For another thing, quite a lot of products now have fanbases just as devoted as any celebrity - which means that brand associations can cement a career in place - rather than weaken it. Appearance in a Nike ad is not simply an exploitation of sporting success - it is as much the final confirmation of it as a gold medal or a world record.

In this case, I have a suspicion that just as many people will be dismayed that Apple has condescended to use mere television stars, as will feel that Mitchell and Webb have sold themselves short.