Key Points:

Last week, Matt Stone and Trey Parker killed the Queen. The creators of South Park, America's most scurrilous cartoon show, capped their newest episode by having Queen Elizabeth II, having failed to conquer America, shoot herself in the head. In its familiar, amateurish-looking animation style, Her Majesty then tumbles off her throne as her brains hit the ground with a wet, plopping sound.

It was a classic moment of outrage from Stone and Parker. But it says a lot about South Park that this was actually one of the least offensive moments of the episode. The show, which is due to screen on C4 in the coming months, focused mainly on a nuclear weapon secretly placed inside Hillary Clinton's private parts.

It is impossible to describe in a family newspaper the indignities then heaped upon the former First Lady as the device was disarmed. Suffice to say, they made the Queen's suicide look tame by comparison.

Even after 10 years, South Park can still shock. The show is now older than the four school children who are its main characters and whose surreal adventures in a fictional Colorado town make up the plots.

South Park has become an American institution. It is loved, loathed and feared. It targets liberals, conservatives and anyone in between. And it does it all with the sort of juvenile, fart-laden humour that the average 6-year-old would find unsophisticated. It is also a work of genius.

Its unique satirical edge has made Stone and Parker household names. Yet these two foul-mouthed jesters have reaped all their successes by throwing mud at everyone, including their bosses.

They see themselves as cartoon punk rockers, tearing down a comic establishment and beholden to no one but themselves.

As it approaches its 10th birthday, South Park is still a show that screams for attention. You may not like it, you may not find it funny, but it is impossible to ignore.

Randolph "Trey" Parker and Matthew Richard Stone come from the quiet, mostly white suburbs that define middle-class America.

Parker was born in Conifer, Colorado, in 1969 and Stone was born in Houston, Texas, in 1971 but later moved to Colorado. They led uneventful lives in hard-working families.

"They had great relationships with their parents," says one friend. Both worked hard at school. Parker was a film geek and music buff who sang in choirs, while Stone was a maths whiz.

The pair met at the University of Colorado in Boulder. They often skipped class to undertake a variety of projects including a film about a Mormon missionary who becomes a porn star and a musical about a cannibal. But it was a cartoon short that launched their careers.

It was called Jesus vs Frosty. Four boys make a snowman who then comes to life and kills one of them (Kenny). So they summon the baby Jesus who decapitates Frosty by throwing his halo at him.

The cartoon caught the attention of a TV executive who paid the pair US$1200 to make a new version (called Jesus vs Santa) he could send out as a Christmas card. It became one of the first-ever viral videos and ended up being watched by most of Hollywood's top brass. George Clooney apparently made 300 copies.

It also caught the attention of an executive at cable channel Comedy Central, who promptly commissioned a show. From then, it was almost as if South Park was born fully formed. That first private video had the main characters, the catchphrases ("They killed Kenny!") and even the anti-religious satire.

The first proper episode was called "Cartman Gets an Anal Probe", and was a huge success. Its first season made the cover of Newsweek and Rolling Stone. The show is Comedy Central's single most important element, despite the fact that its exact profitability remains a tightly guarded secret.

South Park owes everything to its two creators: every episode is a journey into the minds of Parker and Stone. And it turns out that that place is a dark, twisted and highly original landscape.

The four boys - Stan, Kyle, Cartman and Kenny - live in a bizarre alternative universe of a small, permanently snowed-in Colorado town. The inhabitants are deranged, perverse and beyond description. Plot lines involve alien invasions, visitors from the future, talking turds, political revolutions, strange cults, child abuse ... the list goes on. Two of the boys are clear alter-egos of Stone and Parker, with the earnest, sensitive Stan being Parker and the sceptical Jewish Kyle being Stone. Together, the two make a perfect partnership.

"Trey is sort of the creative guy, but he could not do it without Matt. Matt is the big-picture thinker while Trey is a classic creative genius," said Arthur Bradford, a writer and documentary-maker who knows the pair. Of the two, Stone is the one who most regularly fights with his TV bosses.

Parker, on the other hand, would rather stand on the sidelines laughing and then move on. He tends to avoid direct confrontation, though, it has to be said, confrontation comes with the South Park territory.

They spread their comedic guns far and wide. Religion is a regular source of fun, especially Tom Cruise and Scientology. Catholicism came under fire in an episode about a statue of the Virgin Mary that was bleeding (one won't say from where). Judaism is regularly abused. Even the greatest of modern taboos - mocking Islam - has occurred, including portraying Muhammad in 2001 as a superhero who can turn into a beaver.

The defining philosophy in the show is the fight against censorship.

They famously made the point against attempts to censor swearing on television by using the word "shit" 162 times in one episode. Another episode, called With Apologies to Jesse Jackson, used the word "nigger" 42 times.

Each example illustrates the twin strengths of the show. First, it is neither right wing nor left wing. It attacks everybody.

Both liberals and conservatives have tried to co-opt the show to their causes and largely failed.

The way it is produced allows Parker and Stone to control the process from beginning to end.

They write, direct and edit each episode. That gives them remarkable creative power.

It is not all crude jokes. After the Danish cartoons crisis, South Park did a two-episode show called "Cartoon Wars". For those who think South Park is nothing more than scatological humour, Cartoon Wars was an elegant answer.

In the aftermath of the global protests that greeted the depiction of images of Muhammad in a Danish newspaper, Parker and Stone made no secret of their views. In Cartoon Wars, Kyle's character passionately argued the case for a free press in the face of violent intimidation.

Parker and Stone did not have it all their own way on that episode. Comedy Central would not allow them to show images of Muhammad at the end of the show. It was a rare defeat.

Yet the unthinkable is starting to occur. South Park is now growing old, along with its creators. Parker, Stone and their team of writers used to be famous for their wild nights out. Now Parker is married and both lead more settled lives. They are very wealthy and Parker alone owns seven houses.

But their efforts to move away from the show have not been entirely successful. Their satirical movie Team America received mixed reviews.

For now the pair are committed to producing a twelfth series, taking them to the end of 2008. After that, they face a tough personal and professional decision. Do they carry on or quit while they are at the top of their game? After 10 years, South Park is still as offensive and funny as it ever was. Parker and Stone's greatest achievement may be this: when South Park finally ends, it will be greatly missed.

On Screen

* What: South Park
* When: Tonight, 9.30pm
* Where: C4