It's an unsettling experience that unites anyone who has enjoyed the likes of Channel 4's spoof show, Trigger Happy TV.

Perched in front of the television, you are willing the prank along while, at the same time, recoiling with embarrassment for the victim, who is about to suffer a dose of mild public humiliation.

The same goes for watching Ali G lay into one of his unsuspecting interviewees or the late Dennis Pennis sticking a microphone in front of Kevin Costner and asking earnestly: "Why are you so crap?"

More than 30 years after Candid Camera, spoof television is clearly enjoying a resurgence of interest. Witness the success of Mrs Merton, The 11 O'Clock Show, Victor Lewis Smith and The Day Today, in recent years.

Trigger Happy TV is just the latest example. The show is a bewildering string of inspired pranks, played sometimes on members of the public, sometimes on celebrities.

Its co-creator, Dom Joly, stars in all the sketches, hiding behind a range of outrageous costumes.

Joly has said he wanted to "lead people into a state of fairly calm confusion, the equivalent of people sitting in a pub and getting pissed".

Sometimes the stunts are surreal, like when two men, dressed as dogs, start fighting at a bus stop.

Sometimes they set out to lampoon stereotypes, like when Jolly, dressed as a city slicker, interrupts an a cappella recital by bawling, at throat-rasping level, into an oversized mobile phone: "Hello ... I can't hear you, you're cracking up."

The butt of the joke however is nearly always English impassiveness, like when Joly, dressed as a comic book criminal and holding aloft a big sign with the word "robber", walks past two policemen. No one bats an eye.

The appeal of Trigger Happy TV, Ali G, or Mrs Merton is that we all love to be in on a joke that one person doesn't get.

But Peter Watts, TV critic at Time Out, says a "legitimate target" is necessary.

"I have the attitude that celebrities are sitting targets for this sort of programme. They build themselves up and need taking down," he says.

Making the public look silly is a more delicate act - after all it could be you or I on the receiving end. Joly carries it off because his wind ups are fairly subtle, says Watts. The likes of Jeremy Beadle tend to go in more heavy handed and Candid Camera, which started the craze in the 1960s, is just "too smug".

Politicians are a good, if rather obvious, bet. They have been preyed upon by the likes of Ali G and Chris Morris, who many would rate as the king of contemporary spoof television.

"Media terrorist" Morris, however, has perhaps been too cavalier about his targets, chosing to focus on media figures, as well as others. His on-air dig at former Channel 4 chief, Michael Grade, led to a falling out between the two. Grade referred to it as "a breach of the oldest convention in broadcasting" between the editor and the presenter.

Commentators asked whether his capacity for outrage was pushed to the limit last year when Morris penned a spoof diary for the Observer newspaper, in the guise of someone who had set a date for his own suicide. The column, called Time To Go, echoed the published journals of cancer sufferers John Diamond and Ruth Picardie.

But still broadcasters are willing to sail close to the wind with these sorts of acts, maybe because the programmes are relatively cheap to make, attract a loyal audience, and are geniunely funny.

But there is one major drawback that every spoof artist must face up to - the built-in obsolescence of the idea. Put simply, the greater their success, the more likely they are to be recognised, and therefore rumbled.

Beadle tried to crack it with his line in bulky overcoats, dark glasses and beards. It is said that, at times, even Chris Morris's mother could not recognise her son on TV.

"Dennis Pennis just about got out in time. It got to the point where he was being recognised, in Britain at least, by Kris Akabusi, or whoever, and they just refused to talk to him," says Watts.

Caroline Aherne's alter ego, the granny chat show host Mrs Merton, managed to pull it off because her guests knowingly played along.

Generally though, it leaves just one option - to go stateside. It's a difficult transition says Watts, who believes it dilutes the humour.

"Ali G in the States wasn't quite as effective because the people he was interviewing were not really as relevant for British audiences."

Which leaves just one solution for those who have become too famous for their own good - a switch to radio.