Now cartoon character SpongeBob SquarePants is celebrating his 10th anniversary on television, a major milestone for any star. His creators are still mystified at his lofty status as an global pop culture icon who counts US President Barack Obama, actor Johnny Depp and singer David Bowie among his friends.

It has been a surreal, goofy journey for the talking yellow sponge from Bikini Bottom, his pink starfish friend Patrick and greedy employer Mr Krabs.

But SpongeBob's naive optimism, the show's humor and even a brief controversy over his sexuality have merited celebrations this week ranging from a 10th anniversary documentary to the unveiling of the first-ever wax figure of an animation character at Madame Tussauds in New York.

Few behind SpongeBob's July 1999 debut on children's TV network Nickelodeon expected him to win as many hearts as he has.

"The sarcasm or mean-spirited stuff that cartoons are usually about might not translate into other cultures," said Executive Producer Paul Tibbitt, who has been with the show since the start.

"But happiness and optimism - the positive traits that SpongeBob has - translate better. I think people were just hungry for something a little more positive. But I would never have thought it would go 10 years," Tibbitt said.

GLOBAL SPONGE

Marine biologist and animator Stephen Hillenburg, who created the characters, thought the show would be cancelled after its first season. It wasn't until he visited a village in Sumatra a few years ago and saw a schoolgirl with a bootleg SpongeBob book bag that he realized how big it had become.

After winning awards in countries as diverse as Australia, Germany and Brazil, the 11-minute episode series "SpongeBob SquarePants" made its Chinese debut in 2005.

The cartoon has even inspired rides at U.S. theme parks.

SpongeBob emerged largely unscathed after being targeted in a 2005 drive by U.S. Christian groups against homosexuality, in which it was suggested that the cheerful cartoon chap might be gay. Hillenburg said at the time that SpongeBob was "asexual."

President Obama named SpongeBob his favourite TV character, telling TV Guide in 2007 it was "the show I watch with my daughters." Depp and Bowie are among the celebrities who have lent their voices to guest characters over the years, thanks mostly to their children.

Comedians Robin Williams, Will Ferrell and Ricky Gervais will appear as themselves in a one-hour anniversary special to be broadcast in the United States in the fall.

Actor Tom Kenny has lent his voice to SpongeBob from the outset after mimicking for Hillenburg a conversation he overheard from a Santa's elf in a shopping mall.

"It's a dream job. You are this iconic character that people enjoy spending time with, and who makes people laugh. It's great," Kenny told Reuters.