Fans gripe that the animated show is nowhere near as funny as it was in the early glory years of the 1990s. Some predict the big-screen The Simpsons Movie, which opened on Friday, will be similarly disappointing. Others wonder why it took so long for the show to make the leap to theatres.

And distributor 20th Century Fox has stoked speculation about the quality of The Simpsons Movie by keeping it under tight wraps, declining to show it to critics until a few days before its release.

Without giving away details, here's the basic story: Homer dumps waste from his new pet pig into an already polluted lake, causing an environmental crisis that prompts President Schwarzenegger and his evil aide (Albert Brooks) to seal off the town.

Escaping enraged neighbours, the Simpsons begin a new life in Alaska, but they eventually realise they must stand by their hometown of Springfield, which faces an even greater threat.

Groening came up with the idea for his dysfunctional family, as he was about to meet with Fox executives to discuss a cartoon idea. Borrowing the names of his parents and sisters, Groening created the boorish, buffoonish but ever-lovable family that would become the Simpsons.

The show quickly became a cultural sensation, with omnipresent merchandising, voices by Hollywood A-list guest stars and critics that included President George H.W. Bush, who complained that America needed to be more like "The Waltons" and less like "The Simpsons."

That prompted an on-air reply by the show's creators, with Bart asserting his family was like "The Waltons," both clans praying for an end to the Depression.