Stephen Hillenburg says he was always "an ocean freak." As a kid he liked to explore tide pools, bringing home things that "should have been left there and that ended up dying and smelling really bad." He later studied marine biology and taught kids about life in the tide pools.

That was perfect training for what he does now. Hillenburg is creator and executive producer of the undersea world of Bikini Bottom, home to that cheesy yellow, gap-toothed creature SpongeBob SquarePants. The Nickelodeon cartoon airs Monday through Thursday at 8 p.m.

Hillenburg talked to Bridget Byrne at Nickelodeon Studios in Los Angeles, in "the submarine room," where the windows are shaped like portholes.

Why do you think kids like SpongeBob?

I think it's amusing to watch a naive, well-meaning character kind of undo more cynical characters -- kind of like watching Laurel and Hardy or Charlie Chaplin. I think that's why kids like the show -- maybe even why adults like the show, adults who wish they were still kids.

Why did you choose a sponge as the main character? And why is he square?

A sponge is a funny animal to center a show on. At first I drew a few natural sponges -- amorphous shapes, blobs -- which was the correct thing to do biologically as a marine science teacher. Then I drew a square sponge and it looked so funny. I think as far as cartoon language goes he was easier to recognize. He seemed to fit the character type I was looking for -- a somewhat nerdy, squeaky clean oddball.

Is there much about him that is like a real sponge?

I think the realest connection is that sponges are odd and we think of them as odd. I think the connection to SpongeBob is that sponges are the most elastic, changing, plastic creatures . . . and I wanted him to be able to do things that were really magical. So he has these really creative moments when he can re-form himself. But most sponges in the ocean are sedentary: They attach themselves to a rock and sit and filter-feed the rest of their lives, and reproduce, and that's about it. Not that they are not interesting, but they are not that kinetic. They are not mobile. They don't cook Krabbie Patties!

Why does SpongeBob have gap teeth?

After I drew him with those kind of spaced teeth I realized I had those too. But really I think I drew them because of his impish nature.

Does the show have a message?

First of all, we want the show to be really funny. But I think in the end the message is: Treat people the way you expect to be treated. And another connection to any sort of message is that a lot of the stories come out of the personal experience I and the other writers had as kids -- the harsh lessons in life which are usually very funny in retrospect, like maybe what happens when you learn your first curse word and you don't know what it means.

What were you like as a child?

Probably well-meaning and naive like all kids.

How long can you hold your breath under water?

I don't know -- I ate a lot of pizza today so probably not too long!