Meet the Minds Behind 'SpongeBob SquarePants'

March 26, 2010 — -- Welcome inside the No. 1-rated children's show in all of television.

If you're thinking the main character is yellow, you're right... but he's no Big Bird.

This is the world of "SpongeBob SquarePants," a show that's grown into a multi-billion dollar phenomenon so popular it is among the top-rated shows on all of cable television.

Watch the full story tonight on "Nightline" at 11:35 p.m. ET

Steven Banks is the show's head writer.

"'SpongeBob SquarePants' is about a sponge who lives under the sea in a pineapple," said Banks. "He works at the Krusty Krab, he makes Krabby Patties. ...

"Then there is Plankton, who is the evil little bit of plankton who wants nothing more than to get the secret recipe to get Krabby Patties, which will allow him for some reason to take over the world."

Of course SpongeBob is not a sea sponge but an actual kitchen sponge. He works as a fry cook in a place called Bikini Bottom with what you might call a "colorful" cast of characters and assorted misfits.

There's Sandy Cheeks, the squirrel scientist who lives in a bubble; Mr. Krabs, the greedy boss; Squidward Tentacles, the depressed, cynical neighbor; Patrick Star, the dopey, good-natured best friend and, of course, the Sponge himself.

We asked the cast what it was that made the show so popular.

"Funny is funny, [and] the actors are all very good," said Roger Bumpass, who voices Squidward. "The stories are funny, it's maintained its longevity."

Bill Fagerbakke plays Patrick. "I think it's SpongeBob's whimsical optimism," he said, "that he cannot be defeated. I think that has a lot to do with its appeal."

Another key to the show's success is that the humor hits for all age groups, said Clancy Brown, who voices Mr. Krabs. "I think adults these days are very immature," Brown said. "We are keeping them immature."

Tom Kenny, the voice of SpongeBob himself, agreed.

"Luckily, the infantilization of the American culture has worked for us," Kenny said.