Surely a girl.

Has pink parts, can't keep her mouth shut and likes taking big things inside of her.

It's a joke btw! :0P

Since sponges reproduce by budding.. it shouldn't matter.  Sponges aren't very complex animals either so.. they don't have genitila or any distinctive features of a male or female.

Then again, this is a cartoon.  Since Spongebob's parents have referred to him as their "son" in several episodes, I'm going with male.

"In those days spirits were brave, the stakes were high, men were real men, women were real women and small furry creatures from Alpha Centauri were real small furry creatures from Alpha Centauri."

I would guess this passage from The Guide may shed some light on the 3 different genders.... Kirby must be a small furry creature from Alpha Centauri.

Kirby is a boy.
(>'.')>

...I think no1 expect you ever thought about that.
Well you could ask same questions about Pokemons... It ain't man or woman..

obviously its a boy!!

a boy with a fannie!!!

Sponges are sexless, but in the show they are gendered, and SpongeBob is a male.

Kirby might be the same way.  He's definitely a dude.  The first commercials always said "HE'S ONE TOUGH CREAM PUFF!"

For all you guys saying he is a boy.Do you have any prove?I mean he/she is always naked and...you know....

I don't think Kirby has any genitals.. he's just a pink blob.