The Simpsons have reached a landmark 20th birthday and an astonishing 400 episodes of their madcap TV show, and after two decades of 2D fun the stars are still clamouring to be drawn in. Britney Spears, Paul McCartney, Mel Gibson, Pierce Brosnan and George Clooney are among the 297 big names to have made an appearance on the world's longest-running sitcom which this July will explode onto the big screen with The Simpsons Movie.

Even world leaders are getting in on the act.

George W Bush is said to be a big Simpsons fan and his staunch ally Tony Blair admits to being partial to the cartoon family too. Blair says: "I unwind with the kids. We watch TV together, that sort of thing. I love The Simpsons."

Blair even starred in a special episode of The Simpsons in which Homer, his blue-haired wife Marge and their family travel to London on holiday, but the British prime minister, like his best pal George, was a little busy to voice his character himself.

Some of the greatest minds on the planet have also pitted their wits against Homer, whose brainless utterings have become a basis for philosophy in their own right . . . there's even a university course based on the fat yellow fellow. Stephen Hawking is a fan and saved Homer's daughter Lisa from a riot in one episode, while novelist Stephen King has also been enticed to appear.

A guest appearance on the phenomenally successful Simpsons has become a well-trodden route . . . Michelle Pfeiffer, Winona Ryder, Susan Sarandon, Dame Elizabeth Taylor, former X-Files pair David Duchovny and Gillian Anderson and Harry Potter author JK Rowling have all submitted to the animators' art.

So why the stampede of well-known faces, desperate to be scrawled in pen and ink and give voice to their cartoon persona? The answer to that question is one even Homer might be able to formulate . . . viewing figures are upwards of 70 million worldwide ensuring mass publicity and an instant 'cool' tag with fans.

But don't expect the same star treatment as the film-set or chatshow if you are lucky enough to make it onto the biggest smallscreen hit there is. When Alec Baldwin and his then partner Kim Basinger appeared in Springfield they had Homer crashing in through the roof.

It was reported that Basinger enjoyed the joke where she frantically polished her Oscar.

"They thought the script was hysterical, " according to one of the show's producers.

But Baldwin was less amused by a scene where he lands a punch on a press photographer having previously been ordered to pay �2,700 damages after hitting a snapper who tried to get a picture of the couple bringing their newborn daughter home from hospital. "Kim could have laughed a little harder at that one, " observed the same producer.

The show's creator Matt Groening is the man who stands guard at the entrance to DUMBOSOPHY: THE WISE WORDS OF HOMER J SIMPSON "Weaselling out of things is important to learn. It's what separates man from the animals. . .

except the weasel."

"If you really want something in this life, you have to work for it.

Now, quiet! They're about to announce the lottery numbers."

"Ooh, I love your magazine. Especially the 'Enrich Your Wordpower' section. I think it's really. . . really. . .

really. . . good."

"If something is too hard, give it up. The moral my boy is to never try anything."

"Son, when you participate in sporting events, it's not whether you win or lose, it's how drunk you get."

"Just because I don't care doesn't mean I don't understand."

"Marge, old people don't need companionship, they need to be isolated and studied to see what useful nutrients can be obtained from them."

"Ahhh. Donuts. . . What can't they do?"

"Heh Heh Heh! Lisa, vampires are make believe . . . just like elves and gremlins and eskimos."

"If the bible has taught us nothing else, and it hasn't, it's that girls should stick to girls' sports such as hot oil wrestling and foxy boxing."