Two friends walk along a New York street as the camera tracks backwards with them. We catch them mid-conversation, or perhaps they are just used to throwing random thoughts out to the heavens. "Man," says Jemaine, the nattier dresser and taller of the two, with thick black hair and outrageous sideburns and Jagger lips. "Back in New Zealand, I was getting it on with lots of chicks." Bret, whose beard and mop of curly hair in no way disguise his wide-eyed elfin youthfulness, frowns as he ponders this assertion. "Who?" he asks dubiously.

Jemaine: Well, ahh, Sarah Fitzpatrick. Ah, Michelle Fitzpatrick. Claire Fitzpatrick. The list goes on.

Bret: Well, that was all of them.

Jemaine: Well - triple figures.

Bret: No, that's not triple figures. That's three.

Jemaine (ignoring him): Here, though, I don't seem to get with any women. I just talk about getting with women.

Bret: Yeah, but the ones you talk about are hot. They're a lot hotter than the ones you get with in New Zealand.

Jemaine: That's true. I do talk about getting with some pretty hot women.

Bret: You don't just talk about it, man. You talk about it a lot.

Jemaine (proudly): Yeah, I suppose I do talk a lot about getting with some very hot women.

That's the opening moment - no fanfare, no back-story - of last year's pleasantly surprising cult hit Flight of the Conchords, a 12-episode series now running on Channel Ten (Sundays, 10.10 pm). The real Jemaine and Bret are Jemaine Clement and Bret McKenzie, a New Zealand comedy and singing duo known as Flight of the Conchords. Their surreal songs, often explorations of the absurdities of contemporary song-lyric conventions, have long had a popular life on YouTube (check out, for instance, their recent clip called ‘Ladies of the World'), and as a live act Clement and McKenzie have done well around the world. But somewhere at HBO an executive took a punt, and Flight of the Conchords was born: a low-budget, loosely constructed show about two comically hapless, ludicrously innocent friends trying to make a go of it and find gigs - and girlfriends - in bustling, hyperactive New York City.

The two share a small apartment, which allows for much comic interplay in their attempts to make headway in the world of New York dating. In the first episode Jemaine sits on the couch with a girl, and the instant he leans in to kiss her, the light switches on from the bedroom alcove: it is Bret, tucked into his single bed, listening to music on his headphones. "Oh hey, guys," he says. "That's just Bret," says Jemaine. "Turn the light off, Bret." Bret does, but the girl is awkward now, and starts to leave. "You sure?" asks Jemaine, while she hesitates. Then Bret's voice pipes up from the darkness: "So, on or off with the light, then?"

The next morning, it strikes Jemaine that the light-switching incident was the reason for the date having failed. Bret thinks it's more likely to be the fact that he, Bret, had previously gone out with the girl; this strikes Jemaine as being a slightly implausible explanation. Later, the girl suggests that she and Jemaine not see each other again, claiming that it was an Australian she was hoping to find - "Do you know any?" - and that Jemaine had looked good to her only because she had been drunk at the party where they met. "I'm usually more charismatic than this," Jemaine deadpans, missing the point altogether. "Maybe we should have a break," he says, in a kind of forlorn pre-emptive strike. "Break?" she says, incredulous. "But there's no relationship." "Yet," he reminds her cheerfully. "We could start with a break."

This pairing doesn't rely at all on the dynamic of goading and spiking which is the spine of many male comic duos, all the way back to Laurel and Hardy. Traditionally, two conflicting stances drive the comedy: here, the Bret character would hit the Jemaine character harder with the notion that Jemaine is, contrary to his self-image, not quite the ladies' man. Instead, Bret and Jemaine are gently supportive of each other, and throughout the series moments of conflict quickly dissolve into unspoken forgiveness. The two survive in a hostile and impersonal Big Apple not just because their innocence is a blanket of protection around them, but because as comic figures they are somewhat angelic, and transparent, and thus the chaotic world which drives the rest of us so crazy passes through them like light. They don't have great self-knowledge, just curiosity, like four-year-olds or dogs. "After six or seven weeks," muses Bret at one point, "girls find me boring. But I'm not sure what happens, because that's about how long it takes to get to know someone." If innocence were gold, he would be Fort Knox.

They're helped in their endeavours by their band manager, Murray Hewitt, brilliantly played by Rhys Darby. Murray is the Deputy Cultural Attaché at the New Zealand Consulate. We assume he knows a bit more about how the world works, but it's hard to imagine exactly how, so great is his stupidity. Even though he acts as their mentor and guide, it's usually a case of the blind leading the blind. There's a bit of David Brent from The Office about Murray, in that both see themselves as slaves to a bureaucracy while dreaming of greater things, and both fancy themselves as being canny and sharp despite much evidence to the contrary. But The Office is so dark, and sometimes painful to watch, because Brent is fundamentally mean and self-loathing, whereas Murray is filled with the best of intentions, and with an optimism for his charges' prospects that is almost as heroically naive as their own. In one episode Bret, desperate to attract more than three or four punters to their gigs, suggests - somewhat surreally - that they hand out free pencils. "No," chides Murray gently, dismissing the idea like a kind, amused parent. "You're not in New Zealand now, Bret."

Meanwhile, Murray's badly designed travel posters keep popping up, throughout the series, on the walls of his office: generic New Zealand landscapes with text that shows how, as a copywriter, Murray makes a great Deputy Cultural Attaché. "New Zealand - Like Lord of the Rings," one says. Another: "New Zealand - Why Not?" My favourite: "New Zealand - Don't Expect Too Much - You Will Love It."

Australia, more than America, is the target of ribbing in many of these scenes. At the Trade and Migrant Expo, where Murray has secured a gig for the band, the Australian stall is next to the New Zealand one, as always. "But this year," Murray says, "with you guys playing, we're going to blow those Aussies out of the water." Bret, sick of their poverty by now, has found a job holding up cardboard signs on street corners, advertising tailors and computer stores and the like. He will miss the expo, so he substitutes a cassette recording of his guitar and vocals. "Tuck your shirt in," Murray says to Jemaine at the expo. "You look messy. Try and be proud of New Zealand." Jemaine sings, but the Australian stall has the "Wet and Wild Bikini Barbecue Girls Welcome", and it is really no contest. Murray is disappointed and annoyed - but, ever the professional, he does his best to put on a brave face. "We've got a toothbrush fence. Imagine that, a whole fence made out of toothbrushes, sir. And bungee jumping, we've got bungee jumping. New Zealand!"

The comedian Arj Barker plays their friend Dave, excellently wry as the most normal of the gang of misfits. At the other end of the spectrum, the comedian Kristen Schaal is delightfully off-the-wall as the bug-eyed Mel, the Conchords' obsessive follower, who's more than happy to sabotage, in various episodes, the potential arrival of any new female fans. With the help of her long-suffering husband, Doug, she stalks the boys constantly. It only serves to make Jemaine and Bret uncomfortable. Sitting between them in the back seat of her car, having offered them a ride (Doug is driving, of course), Mel says suddenly, breathlessly, "Oh man, the car could just burst into flames right now and this would be the way to go. Huh, guys?" "Just here, thanks, Doug!" Jemaine shoots back, ready to jump.

Beyond its core of great characters, Flight of the Conchords is notable for its brilliant songs. Clement and McKenzie are master pop-deconstructionists, and each episode contains two or three songs that burst out from the narrative, often at the most unlikely moments, so in a broad sense it's a musical comedy. There are riffs going in all sorts of directions: Gary Newman, Grandmaster Flash, the Bee Gees, Bowie. Both singers have an extraordinary range - Clement in particular, who seems to move effortlessly from baritone to soprano - and they do a great business in point-counterpoint, taking alternate lines in strange directions and cramming words into lines that can't contain them. The initial direction of a song - social commentary, say - will get hijacked by one absurd or overly lateral thought after another: "They're turning kids into slaves just to make cheaper sneakers / But what's the real cost, 'cos the sneakers don't seem that much cheaper? / Why are we still paying so much for sneakers / When you've got little slave kids making them? / What are your overheads?"

There's exuberance in the way they lay bare the neurosis of thinking out loud, and in so doing expose just how rigid and restrictive is the language of pop:

Looking round the room

I can tell that you

Are the most beautiful girl in the room

(In the whole wide room, ooh)

And when you're in the street

Depending on the street

I bet you are definitely

In the top-three good-looking girls on the street

(Depending on the street, ooh) ...

You're so beautiful

You could be a part-time model

But you'd probably still have to keep your normal job

Along the way, Jemaine and Bret delicately glorify the absurd, cavorting through what is surely the most whimsical exploration of the sweetness of friendship currently on television.