His comedy partner is cooler, more intelligent and better looking. But teenagers of taste love him anyway

Walk into a secondary school a few years ago and it was even money that within 10 minutes you'd find a child pointing at a disgusting object (tapioca / dog's mess / vomit) and saying: "That's you that is," the catchphrase from Newman and Baddiel's History Today. Nowadays you're more likely to hear the comedy-savvy 14-year-old complain that the person they're addressing wants "the moon on a stick", one of several catchphrases coined by Stewart Lee and Richard Herring, creators of BBC2's Fist of Fun.

"Don't mention Newman and Baddiel," a friend advised me before I went to meet Herring. It's become such a reporter's cliche that the duo even have a routine about such "lazy journalistic comparisons". Yet whereas Newman and Baddiel never appeared together very much, Lee and Herring's shows are almost entirely about their on-stage (and, by implication, off- stage) relationship: more like that other double act not so often likened to N&B, Morecambe and Wise. In one respect, however, the comparison still holds: Lee and Herring have the same effect on 13- to 20-year-olds that catnip has on cats. They are the teenager's comedy drug of choice.

Since we live in the age of the anti-hero, the ordinary bloke with ordinary worries and weaknesses, it's Herring - the short, podgy, 29-year-old going on 16 from Cheddar in Somerset (son of Keith, the caravan-owning retired headmaster) - rather than the moody, good-looking Lee, who one suspects is more in tune with the times. With Fist of Fun, which has now completed two BBC2 series after a lengthy apprenticeship on Radio 1, Lee and Herring brought viewers "the blinkered perspective of two emotionally stunted and slightly odd blokes in their twenties who live in separate but equally unpleasant rented accommodation in South London". But it's always Herring's character who has been the most emotionally stunted. He's the one unable to maintain a relationship, who has sexual fantasies about Julia Sawalha (who plays Saffie in Absolutely Fabulous). In the latest Lee and Herring stage show, he's even reduced to masturbating over a cow that is being incinerated. All of which begs the question: where does the fictionalHerring (jovial but also puerile, uncool, stupid, drunken, slacking, lecherous and obese) end and the real one begin?

The real Richard Keith Herring sits in a cafe off Leicester Square in London and just laughs, a rich, boyish, Somerset chuckle, when asked whether he's like his character. What is immediately evident is that, on the one hand, he's just come from Harvey Nicks where he's been buying a suit for a wedding (not at all a "fictional Herring" thing to do); on the other, he does have a hangover (a very "fictional Herring" thing to have). It's also obvious, even on the briefest of meetings, that he can exercise a fair degree of charisma. So doesn't he mind that Lee is often perceived as not only more intelligent (you wouldn't find Herring being invited to discuss what he's reading with Sarah Dunant on Radio 4), but also sexier? Isn't he a little bit jealous?

"To be honest, I don't think it's really like that," says Herring. "When we get letters from girls we get 50-50. We just appeal to different kinds of people. Stewart gets more angsty girls writing with their problems, and I get more bubbly people writing and sometimes [again the chuckle] offering sex. I think saying I'm a failure with women endears me to certain types of women. But then we don't get a lot of fan letters like that. Not as many as Frank Skinner." What about Lee's apparent coolness, though? What does a man who admits "quite a good evening for me is sitting on my own watching telly in my pants, or playing a computer game" make of that? "Certainly Stewart is cool. But what's cool? Arthur Fonzarelli's cool - for a bit. Then he's a joke. The Knightrider's cool. Then he's a joke. I know for a fact that Stewart's not as deep and exciting as some people imagine." At this point, as if to underline Herring's indifference to all things of the moment, the actor Tom Watt, Lofty from EastEnders circa 1987, wanders into vision and distracts him. "See, that's the sort of thing that happens to me," he says. "I get star struck.

"Occasionally," Herring reflects, returning to the matter in hand, "we do get a letter where someone will go: 'Oh Stew, you're really cool and good-looking. Why do you hang around with that Richard Herring? He's stupid and fat'. And you just laugh at it. One of the many good things about Stew is that, although I think his coolness really matters to him, he genuinely doesn't mind having the piss taken out of it. Almost without knowing it, he's taking the piss out of himself.

"In the stage act I'm cleverer than I am on television, and I can try to make him look an idiot. I can have a go at his hair. If David Baddiel had done to Rob Newman what I do to Stew, they would have split up immediately. They did take themselves very seriously." Anyway, he adds, he and Lee have been writing and performing together for 10 years now, since they met through the Oxford University Revue, and they've managed to stay friends.

Try to define Lee and Herring's comedy and you come up against a series of "nots". They're not cult comedy ("That's a stupid term," says Herring. "It just means it's not as popular"). They don't actually tell jokes any more. And, of course, they're not like Newman and Baddiel. Do they in that case share something with Men Behaving Badly's Clunes and Morrissey? "We sometimes get lumped into lad comedy. We like the European Cup [sic], but we're not really into football at all and we're not into cars. I've never owned a car. I like Men Behaving Badly, but I think the laddish thing just turns men into stupid stereotypes. There's more to it than that. In the show last year ["Richard Herring is All Man", a one-man piece he took to Edinburgh] I was saying, 'I like drinking and I like women, and when I get drunk I chase after them - but here's how I feel about my father, and this is how I feel about waking up in the morning and doing something really stupid last night'. In Men Behaving Badly that doesn't really happen."

I remind Herring that he once said: "The annoying thing with comedy is that I partly do it to look cool and appeal to girls, but then I attract all these people who are like me when I was 13." Does it still annoy him? "I do find it bizarre that we've got a lot of teenage fans, but that's just the way comedy works. When I was 12, I had sublime comedy taste. Probably better than I do now. Obviously the people who write to you tend to be teenagers, because they tend to have a lot more time on their hands. I know it's probably Stew they think is cool but the idea of teenagers having my poster on their wall and listening to what I say ..." He dissolves into giggles. "I'm 29. If I'd got married nine years ago then had a kid, it would have been even more ridiculous. It's quite nice in a way, though. It keeps us in touch."

In touch Lee and Herring may be, but that doesn't mean that they are going to let their young audience grow complacent on the easy adulation that catchphrases invite. "You can build an audience just by saying 'moon on a stick' for half an hour. But we think it's a bit of a rip-off. I do a thing in the live show where I just keep saying to Stewart, 'You want the moon on a stick' over and over again, until it becomes really annoying. And then I say, 'That's all the audience wants, Stew. They're stupid. All they want is for me to say you want the moon on a stick, and for you to deny it'."

It would be nice to think that such daring went rewarded. But, then again, it would be nice to think you could get the moon on a stick.

"Lee and Herring Live" is at The Pleasance Theatre, Edinburgh until 25 August (0131-556 6550). A 40-venue national tour follows in the autumn. Richard Herring's "Punk's Not Dead" is at the same venue until 31 August (not 13 or 27 August).