Picture this: A large yellow sponge, with big round eyes and square brown pants, calls a fancy Hollywood restaurant and asks for the best table in the room, okay?

Tom Kenny laughs at the prospect. Not happening, he says. "If you call a restaurant and say that you're the voice of SpongeBob, they'll just hang up on you. I live in Los Angeles. 'SpongeBob? We've got Jack Nicholson coming in!' "

For the past five years, Kenny has been the sound behind the most famous sponge in history. The character he helped create with "SpongeBob SquarePants" originator Stephen Hillenburg has become a cultural icon, a touchstone of humor, a mega-selling product and the most successful cartoon that Nickelodeon has aired. And its audience goes beyond the kids for whom it was intended: 30 percent of the viewers are over age 20, according to Nielsen Media Research.

On Friday, Mr. SquarePants became a movie star, too, when the first "SpongeBob" full-length movie opened in theaters.

SpongeBob lives his life going happily through every surprising day with his best friend Patrick, the not-very-bright starfish; Sandy Cheeks, a squirrel looking for excitement; his money-loving boss Mr. Krabs, and the cranky neighbor Squidward. In the movie, the plot has more spins than a backward 31/2-somersault pike, venturing out of the safety of Bikini Bottom and into The World. Suffice to say that SpongeBob must battle the evil Plankton's plot to take over his happy home town, and David Hasselhoff of "Baywatch" fame is his greatest ally.

The reviewers may think what they want, but my 9-year-old son proclaimed it "the best movie I have ever seen, and I have seen 'Top Gun.' "

That made Kenny laugh and laugh, in his own, non-SpongeBob voice. He is quick to note that the character's voice is not electronically altered, as many people assume. He does, he says, use his hands to help make SpongeBob's signature laugh, something that might sound like a maniacal sheep.

"It's probably a good thing you can't see me right now," he says by phone from Los Angeles. "I just make a kind of weird smoky noise in the back of my throat -- EHHHHHHHHH -- and I move my hands up and down on my Adam's apple. BAAHHHAAHHHAHAHA. It's very bizarre. I never knew I could do that until SpongeBob. There are very few jobs where that skill is going to come up."

Hillenburg tapped Kenny for the voice of SpongeBob when he was still in the process of creating the cartoon.

"He and I had worked on an earlier cartoon for Nickelodeon and that was the first time either of us had been hired to work on an animated cartoon," Kenny says. "We just hit it off. When it came time for him to pitch his own show, he had this idea that had been percolating in his brain about this sponge that lives in this pineapple and works at this restaurant.

"Before he pitched the show to Nickelodeon, he and I got together a bunch of times. We just worked out what the character would sound like and what he would laugh like and where his voice placement would be. One of the great things for me about SpongeBob is that I didn't have to audition.

"Most of the time you walk into a room to audition for a cartoon and there are 15 or 20 of the best voice-over guys in the business sitting in the waiting room, and you just go, 'Ohhh boy. This is not going to be easy.' "

Kenny is 42 and married with two young kids (a son, 7, and a daughter, 15 months). He grew up in East Syracuse, N.Y. After high school he took a year off to find himself and, he says, is still looking. He moved around a bit and landed in Los Angeles in 1992 when he started getting more acting work.

But ask him if he had a plan for his life and the answer is definitely no.

His son's school "asked me to come and do career day," he says. "I was like, geez, I'm not sure. Are you sure you want me to come to career day? I make a living being silly. Do you want to encourage that behavior in your first-graders?"

SpongeBob, who shifts between being a kid and an independent adult with a job (Krusty Krab fry cook extraordinaire) is "a combination of a child and a grown-up," says Kenny. "And that's definitely what I am."

As a kid Kenny was a self-proclaimed "animation freak," watching "Rocky and Bullwinkle," "The Jetsons," "Top Cat," "Yogi Bear" and others.

"I was fairly shy up until seventh or eighth grade. People say, 'You must have been the class clown.' I was too shy to be the class clown. I was the class clown's writer. I would pass jokes to the class clown and say, 'Hey, say this during math class.' "

By 17 he was doing stand-up comedy in clubs. That turned into acting and eventually voice work. He's been Heffer in "Rocko's Modern Life" and Dog in "CatDog." And he does the voices of Elroy Jetson and Top Cat for promotional spots for Cartoon Network.

Kenny has written three songs for the soundtrack, with the SpongeBobian titles of "Employee of the Month," "Under My Rock" and "Best Day Ever."

"The reason I was able to write those songs and sing those songs was because as a teenager, I played in rock-and-roll bands with my friends. Obviously I never made a living at it and never became a rock star, but I pursued something I was interested in.

"Years and years later, it comes in handy. I guess all those hours in the garage driving my parents crazy with band practice wasn't wasted. Nothing is wasted."

As for his famous character, Kenny has a great fondness for him and his ability to make kids laugh. Although the idea behind the cartoon is simply to be funny, if there is a message to kids from the little yellow guy, Kenny says it would be something like, "Be enthusiastic, live life, every day has the possibility to be the best day ever. SpongeBob comes out of bed every day and says, 'This is going to be the best day ever!'

"Sometimes it is and sometimes it isn't. But it's a nice way to start the day."

Nickelodeon's deep-sea cartoon star rises to the big screen's surface in "The SpongeBob SquarePants Movie," as does the man who voices him, Tom Kenny, right and below (with Scarlett Johansson, also in the film.)