The Mighty Boosh, once a cult comedy duo, now have stage and TV shows, a travelling circus, their own festival and an utterly obsessive fan base. In January they will be the first comedy act to play Dublin's 02. The "Led Zeppelin of comedy" talk to Brian Boyd.

THE MIGHTY BOOSH surrealist comedy duo of Julian Barratt and Noel Fielding took their name from a nickname - "The Mighty Bush" - given to Fielding's brother, Michael on account of his big, afro hairstyle. This is only important to know in the context of President George Bush's visit to Northern Ireland in June of this year. While visiting a school, George Bush received a present of a pot plant from the children. A photograph shows the US President holding up his plant - which is called "The Mighty Bush" - and a group of school kids sniggering in the background.

For Barratt and Fielding it was a "we've made it" moment. Their weird Dadaist-inspired show, which had begun 10 years ago in dingy London comedy clubs, had reached the stage of a massive in-joke at the expense of the leader of the free world.

The Boosh now stand at a creative crossroads. They have long since outgrown their cult status. Thanks to a series of award-winning stage shows, some beautifully-inspired and executed TV series, a fervent and obsessively dedicated fan base and a travelling road show (they will be the first comedy act at Dublin's 02 when they perform on January 5th) which repositions them as comedy's Led Zeppelin, the Boosh could go either way: gently implode like that other wacky comedy duo Vic Reeves and Bob Mortimer did, or become a global franchise.

"The Boosh have mutated so much," says Julian Barratt. "It's this big rock 'n' roll juggernaut now, whereas not so long ago we'd be playing to 20 people, half of whom would walk out after 20 minutes, thinking us to be some elaborate Dadaist prank."

People's reactions are understandable. Barratt plays ex-zookeeper Howard Moon, a hesitant and awkward jazz aficionado; Fielding plays Vince Noir - a childish lysergically-enhanced David Bowie figure who's almost fatally optimistic and cheerful. Throw in Naboo - a freelance shamen, recreational drug user and magic carpet rider, Bollo - an anthropomorphic ape whose catchphrase is "I've got a bad feeling about this", and Old Gregg, a transsexual monster, and you can see their act is at a bit of a remove from the orthodox.

"There are quite a few yetis in there also. That's important to emphasise," says Barratt. "We like to describe the show as a psychedelic meteorite of music and mayhem. It's easy shorthand."

Weirdly, when Barratt first met Fielding in 1994, they wanted to be the "new Goodies".

"Noel comes from an arty background, whereas I was more into music," says Barratt. "We were both doing the stand-up circuit together and we sort of liked each other's routines and found we had a lot in common. A lot of what people take for the 'weirdness' of The Boosh is there simply because we were broke back then and for props we would use an old pair of curtains; and we'd use polo mints for eyes. Coconuts were always a favourite prop - they were relatively cheap and easy to get hold of. When the show began to take off, we never bothered upgrading the props and the 'disguises'. It's how people see the characters now so we couldn't change them. But it is weird when you're playing the O2 Arena in London and there's all this security around - you feel like Prince - and then you reach for a pair of Polo mints to go out on stage with."

There's a quote from the Belgian surrealist artist René Magritte about his work - "My painting is visible images which conceal nothing; they evoke mystery and indeed, when one sees one of my pictures, one asks oneself this simple question: 'What does that mean?' it does not mean anything, because mystery means nothing either, it is unknowable."

It could double as a mission statement for The Boosh. Magritte is an overriding influence (however much in the background) and is evident in the way they often place ordinary objects in an unusual context.

"That's exactly what The Boosh is," says Barratt. "It's the juxtaposition of surrealism with the commonplace done as a sort of magical narrative. It's creature-led oddness. But I really hope that it's not oddness for the sake of oddness. I think we're pulling off the same tradition as The Goons and Monty Python. Yes, what we do is 'weird', I would be deluding myself if I thought it was normal. But I don't think we're not unrepresentative of normal people - if you know what I mean."

Barratt is a middle-class Yorkshire man, Fielding is a working-class Londoner. Their Boosh characters of Howard Moon and Vince Noir are blown-up characterisations of their real identities: Barratt is the quiet, shy one who listens to jazz; Fielding is the exuberant party boy around town. Neither can get his head around the fact that The Boosh seem to have become less a comedy act and more of a "movement".

"It was just going up to Edinburgh year after year and trying to make an impression," says Barratt. "We always knew a certain amount of people were going to say, 'this is absolute rubbish - they're taking the piss', but we also hoped that there would be some cool indie or arty kids who might go 'this is great - everyone else hates them so we're going to love them' and it was just a case of one faction outweighing the other. Because of doing well in Edinburgh, we got picked up to do a BBC radio series. Then we got onto television - first BBC3 and now BBC2. Then it just seemed to go ballistic."

So much so that promoter Vince Power got them to stage their own outdoor Booshfest festival earlier this summer. "That was quite something - over 20,000 people, the majority of them dressed as characters from the show, descending on this farm in Kent. We had Jarvis Cocker, The Kills and Gary Numan playing on the bill also, which took the pressure off us a bit," he says.

For Barratt, having their name over a festival, no matter how daunting, had a kind of logic to it. "It sounds a bit weird, but we can be seen as more of a 'feeling' than a comedy act. There's a Boosh album going to come out, there could be a Boosh art exhibition, a Boosh movie. It would be us putting a veil of Booshness over things.

"It's hard to describe properly. But this is why, unlike I'd say a lot of comic acts, we've no problem playing venues such as the O2. We've got music and visuals and all of that. The people dress up as the characters. It's a celebration of weirdness maybe. Maybe people come for the spirit of the show as opposed to the actual content. I'll settle for The Boosh as a 'movement'. Except, imagine the two of us trying to lead anything. Life was a lot simpler when people used to call us 'the new Morecambe and Wise'."

• The Mighty Boosh play Dublin's O2 on January 5th