'What happens if the ad works? What if the theatre is filled with lagered-up youths looking for recreational gore? They will surely find the experience disappointing'

You may have seen the posters on bus-stops: a reddish background on which appears an obscure slogan and an oddly shaped Hula-Hoop (the annular comestible, not the Fifties gimmick). "Oi, Zebedee. No!" for example (accompanied by a spring-shaped Hula-Hoop) or "Oi, Judge Dredd. No!" (accompanied by a Hula-Hoop shaped like a chunky gold ring). Now, it's hardly news that advertising is a frantically allusive medium, but even so, these posters seem to push the envelope a bit. The list of things you have to know before you "get" them is not only a long one but it's also nested, like a set of Russian dolls. So it's relatively easy to imagine someone who might be missing one of the clues. Anyone, for instance, who doesn't know that the Magic Roundabout is a popular children's television show and that it includes a tomato-headed bedspring called Zebedee. Such a person might think, "What does a biblical tax-inspector have to do with potato snacks?" Another might easily be baffled by Judge Dredd and even more so about what exactly it is he's being warned not to do. Even when you've worked out the names there's still a mystery - this isn't ordinary celebrity endorsement, after all. And though Harry Enfield appears in the television ads to which the posters form an accompaniment, he appears in character, a spin-off from a running joke on his recent television series (the sketch involved two pub drinkers, fantasising about how they would react with undazzled sternness should a celebrity ever attempt to take liberties. "Oi [name]. No!" was the catchphrase that resulted). Even now, we're still not quite there - the association of belligerent stupidity with junk food is easily graspable, it's true, but why should it be thought a sales pitch?

The explanation involves two old advertising tropes - firstly, the suggestion that your product is such as to inspire a fierce protectiveness in the consumer (remember "Watch out - there's a Humphrey about"?) and secondly, the perennial appeal of catchphrases. The sellers' dream is that the appetite for a snack might prove as contagious as the fashion for a slogan; they hope to raise the value of their product in the playground's stock exchange of coolness. And there's a nice appropriateness to the method - what better than "word of mouth" to sell crisps? There's another campaign currently running which aims at the same common touch but demonstrates how wrong you can get it. A blood-boltered face, distorted in a vampiric rictus, is surmounted by a horror-film typography (the letters look as if they have been scratched out by claws). Beneath the title runs the slogan - "A Natural Born Killer Too". This is the Royal Shakespeare Company's current poster for Coriolanus. Unlike the Hula-Hoop ad, which hits its target in the bull, the Coriolanus is a deliberate attempt to aim off, employing a demotic voice for a product that has almost no demotic appeal. (This isn't to say, incidentally, that Shakespeare has no attractions for the unlettered, should the two happen to come into contact, just that a common touch isn't the principal appear for its natural market). This isn't exactly new either - Max Reinhardt's 1935 production of A Midsummer Night's Dream, starring Jimmy Cagney as Bottom, was sold with the slogan "Three Centuries in the Making". But A Midsummer Night's Dream was at least a film, which clearly had to be marketed to film audiences. The RSC is trying to do something different - to sell a play as if it is a video nasty. You can see that the method might be adapted for other plays, too - what about Titus Andronicus ("Guess who's coming to dinner?") or Othello ("Guilt is never just a black and white affair") or The Merry Wives of Windsor ("He would give them a knight to remember!"). But what happens if the ad works? What if the theatre is filled with lagered-up youths looking for recreational gore? They will surely find the experience disappointing. Perhaps the RSC should take advice from Hamlet. "The play I remember pleased not the million," he says, recalling a box-office flop, "'twas caviar to the general." And you can't sell caviar as if it was junk food.