Spongebob is a fry cook at the Krusty Krab. He has always wanted to be a fry cook (his first words were "May I take your order?"), and he's good at it, although Jim (who was the first fry cook at the Krusty Krab) says he won't be great until he strikes out on his own. Still, he beat King Neptune himself in a burger-making contest.

Spongebob is in a gray area as to his age. He has to be an adult, because he has his own house and a full-time job, but he has many childlike qualities. He enjoys blowing bubbles, playing with cardboard boxes, and other silly things kids like. His other big hobbies are karate and catching jellyfish. He's a really nice guy, though he can be annoying (mostly to people who aren't in touch with their own inner child). His best friend is Patrick Star.

Spongebob either has no sense of what other people really think, or he has such a good sense that he sees past what they pretend to think, and into their real feelings. His biggest weakness (besides being a total wimp on the physical front) is that he can't drive. He's taken the test 39 times (a later episode said he failed driving school over a million times) and has the oral exam memorized, but once he gets behind the wheel, he just can't think.

Patrick doesn't have a job; in fact, he won an award for doing nothing longer than anyone else. He enjoys all the same silly games as Spongebob, as well as jellyfishing. Sometimes he comes across as a frat boy for the way he likes to party - and he did state at one point that he'd gone to community college, although he didn't mention what he studied. Usually he seems stupid, though sometimes he seems to know what he's talking about, and he occasionally does or says something very intelligent.

Many have speculated that Spongebob and Patrick are not just friends, but gay lovers. I will concede that Spongebob often comes across as gay ("My weekend was fabulous, thanks for asking!"), but Patrick usually doesn't. And I will concede that the scenario he set up for Patrick on Valentine's Day was very romantic. But I think, for the most part, that people who think these two are lovers just can't imagine that men can love someone other than a relative without it becoming sexual. Because they truly do love each other, and calling them "just" friends is, I think, belittling to friendship on the whole. See also Lord of the Rings.

Squidward (a name based on Edward) is a cashier at the Krusty Krab and lives in between Spongebob and Patrick. He is almost always miserable and/or annoyed. He wants to be an artist of some kind; he plays clarinet, does interpretive dance, and dabbles in many different visual arts. Unfortunately, he's not very good at any of them, most likely because he's too wrapped up in "rules" for art and doesn't let his free-form creativity get out.

Squidward's biggest problem, however, is that he has an idea in his mind of the kind of person he thinks he should be, and doesn't realize he isn't that kind of person. In fact, when he moved to a town full of that sort of person, he quickly got bored and fed up with them. In reality, he likes Spongebob and Patrick and enjoys the childish games they play, but he won't admit it because it doesn't jive with that image in his head, so it makes him angry whenever they distract him from what he thinks he should be doing, and will let them goad him into joining, mostly claiming he's trying to prove he's better than they are.

He does have a cruel streak; one example is in "Naughty Nautical Neighbors," in which he actively set things in motion to ruin Spongebob and Patrick's friendship, then sat down in a lawn chair to watch it unfold.

He is not a squid, but an octopus; he only has 6 arms because the animators couldn't figure out a good way to draw all 8.

Sandy is a squirrel from Texas who for some reason decided to build a dome and live in the ocean. She's good friends with Spongebob because they both enjoy karate. She's very athletic in other areas as well: surfing, weight lifting, running, etc. She's also a scientist/engineer, having built her own rocket to go to the moon (where she said she'd been before) and several sci-fi type devices.

Voice actor Carolyn Lawrence said she took inspiration from Holly Hunter to do this character.

Mr. Krabs is the owner of the Krusty Krab and inventor of the formula for the famous Krabby Patty, which is supposed to be so good that the only people who don't like them have never actually had one. His favorite thing is money; he has the first dollar he earned framed on his wall at home, and he made Spongebob and Squidward stay on a boat and starve until they got his millionth dollar back from a clam that ate it. He often cooks up crazy schemes to make more money (for example, converting the restaurant into a hotel) and rarely notices that he spent more on the scheme than he got out of it.

He used to be a sailor, and he likes to tell sea tales on dark nights. He also has a daughter, Pearl, who is a whale (no explanation is ever given, to the best of my knowledge). This is a major source of conflict in his life, because she's a teenager and therefore feels it's the end of the world if she doesn't have the same expensive stuff all her friends have.

Plankton is a rival restaurant owner, but no one ever eats at his place, the Chum Bucket. (Chum is a variety of salmon, by the way.) He is constantly trying to steal the recipe for the Krabby Patty, and often uses wacky scientific gadgets to do so, though he never succeeds. He and Mr. Krabs used to be friends, until they had a falling out over how to run the restaurant they had together. He is married to a computer named Karen.