By Martin Rosenbaum Producer, Whose side is Bart Simpson on?, BBC Radio 4

"I will not instigate revolution." That's what Bart has to write out repeatedly in an early episode of The Simpsons, which traditionally begins with him chalking up punishment lines on the class blackboard.

The Simpsons recently celebrated their 400th episode

It went along with the notion that The Simpsons was a subversive show which annoyed teachers, parents and the establishment.

But is Bart still a rebel, or nowadays would he write instead "I must not uphold family values"?

The Simpsons has certainly revolutionised animation and its role in popular culture.

The TV show has now reached a remarkable 400 episodes since starting in 1989.

The designs and catchphrases of the characters ("Doh!") are instantly recognisable to a worldwide audience.

Outrage

And next month the first Simpsons movie will open with enormous publicity across the globe, after a premiere in an American town that shares the name of the show's fictional setting Springfield.

This is quite an anarchic and liberal-left assault on that idea of the family, but it's done with great humour and although ideological, it isn't preaching Andrew Neil, who brought The Simpsons to the UK Simpsons quiz

When it began it also caused outrage from some authority figures.

American schools banned pupils from wearing Bart's famous "Underachiever - and proud of it, man" T-shirt.

The first President Bush proclaimed "We're going to strengthen the American family to make them more like the Waltons and less like the Simpsons".

Soon afterwards the show retaliated when Bart responded, "We're just like the Waltons, we're praying for an end to the depression too".

"It's a parody of the conservative paradigm of the nuclear family," says Andrew Neil, who brought The Simpsons to the UK when he was head of Sky Television in the early 1990s.

"This is quite an anarchic and liberal-left assault on that idea of the family, but it's done with great humour and although ideological, it isn't preaching."

Hapless teachers

That represents the world view of Matt Groening, the talented underground cartoonist who created the show for Twentieth Century Fox when Rupert Murdoch's Fox television network was desperate to make its mark.

Groening says the basic message of the show is that those in authority do not necessarily have your best interests at heart.

Inevitably success makes you part of the establishment Tim Long Simpsons writer

Victims of the show's ridicule include the hapless teachers who cannot cope without their teachers' guides, the corrupt Kennedyesque town mayor, the incompetent police chief, not to mention the arch-capitalist owner of the local and rather dangerous nuclear power plant.

But while it annoyed many conservative and religious groups at the start, the show now seems to be finding fans on that part of the political spectrum.

And not just because Groundskeeper Willie described the French as "cheese-eating surrender monkeys", a phrase enthusiastically adopted by some American neo-conservatives in the run-up to the Iraq war.

'Family and faith'

The Simpsons family eats together, plays together, prays together and stays together. Perhaps it's not so dysfunctional after all.

"It seems to be oppositional but at its base it's a very conservative show," says Mark Pinsky, who has written a book called The Gospel According to the Simpsons.

"Your family and your faith are the only things that will defend you from the crushing nature of American society."

Simpson's creator Matt Groening likes to challenge authority

So what do the show's writers make of this?

"It's hard to be Che Guevara forever," says Tim Long, who is part of the writing team.

"Inevitably success makes you part of the establishment."

But he insists they haven't lost "the desire to spew venom on everyone and everything".

He maintains "anything we can make fun of, we will make fun of".

'Different dynamic'

Others think the show has changed and, for better or worse, lost its most vicious and subversive edges.

"In the earliest episodes there's a different dynamic in the family, it's nastier," according to Professor Paul Cantor, author of Gilligan Unbound: Pop Culture in the Age of Globalization.

"There's an early episode where the Simpsons have got to go to counselling and are set up in a system where they can give each other electric shocks and they do it with great glee.

"They wouldn't write an episode like that any more."

So perhaps in one sense The Simpsons have grown up.

Bart may still be 10, the age he was when the show started 18 years back, but like most youthful rebels, he is not quite the provocative and outrageous character he once was.