An outgoing sea sponge who lives in a pineapple under the sea, as the show's Theme Tune implies. Works as a fry cook at the Krusty Krab. Although not very bright, he has a good heart and constantly strives to help his friends...even when they don't really want it.
Ambiguously Gay: Parents made a big controversy of his sexuality after the movie and the episode where he raises an Oyster with Patrick. The writers have since said that he's canonically asexual, though they do slip in a few lines containing some Homoerotic Subtext. It gets more and more exaggerated as the show goes on.
And Call Him George: His attitude towards Squidward, Mrs. Puff, Gary, Barnacle Boy... everyone in Bikini Bottom at some point or the other.
Signature Laugh: It's annoying, but so much a part of his character that it alone is enough for one to recognize him.
Asexual: Stephen Hillenburg plays around with this quite a bit. He mentions that Spongebob is asexual, but since actual sponges usually (though not always) reproduce by budding, he could be referring to the biological aspect only. Because there's little indication in-series that he's ever attracted to anyone, he might be asexual in orientation as well.
Mentions that he has a crush on Sandy could mean one of four things: he is asexual but heteroromantic note (Not sexually attracted to anyone, romantically interested only in the opposite gender.) , demisexual, biologically asexual but heterosexual in terms of orientation, or...it's simply Ship Tease, an accepted staple of any show.
If an episode focuses solely on Spongebob (Picture Day and Blackened Sponge, for example) something bad is almost certain to happen to him.
Captain Oblivious: Taken Up to Eleven in "A Pal for Gary," in which, even after seeing Puffy Fluffy's monstrous true form firsthand and nearly being eaten by him, he fails to notice anything amiss. A more notable example is his complete inability to understand that Squidward is not his best friend and in fact hates him to the point of madness.
Detached Sleeves: Rare male example. Probably not intentional (they supposed to be part of his shirt, apparently), but due to his Abnormal Limb Rotation Range, they're not actually attached to his shirt. During the few times his "square pants" and shirt are torn off, he keeps the sleeves.
Determinator: He may be a pushover most of the time, but nothing will stop him doing his duty for the Krusty Krab, whether it's delivering a pizza or saving his boss from execution.
Genius Ditz: He can flip burgers to suit a royal palate! A running gag is that he's also great at math. If he focuses, he can be really smart.
Drives Like Crazy: Probably the king of this trope in Western Animation. In early episodes, he states that he does know how to drive, but he always ends up panicking behind the wheel and cannot concentrate. Due to Flanderization, it deteriorates to the point where, whenever he gets behind the wheel, he's a Driving Disaster Area
However, a recent, post-movie episode that did not involve boating school featured him driving a truck WITHOUT A LICENSE and WITHOUT problem.
Drill Sergeant Nasty: When training Gary for the Snail Olympics, he puts Gary through Boot Camp training.
Epic Fail: Poor guy managed to get fired five times in one day.
Extreme Doormat: Has shades of this, particularly around peers such as Mr. Krabs, often making him a convenient patsy. Occasional stories show him attempt to gain abrasive skills, only to decide he is happy being "aggressively nice". And it's almost impossible for him to say no to Sandy.
Healing Factor: Being a sponge, he can regenerate lost limbs. This is exemplified in an episode where he removes an arm and a new one pops up in its place. He then removes his other one, and the process repeats until he has a wall of arms holding arms.
Strangely enough, he can even regenerate his internal organs as well. Because of this, he could theoretically be a good organ donor.
Horrible Judge of Character: Spongebob thinks that Squidward is a good friend of his and that Mrs. Puff is a nice teacher willing to help him, when both could not be further from the truth.
Hypocritical Humor: Anytime he is forced to put up with someone as obnoxious and clingy as himself, he will become as irritable and neurotic about their lack of consideration as Squidward does about him.
Idiot Houdini: To the point when he gets away with making Squidward and Mrs. Puff's lives a living hell.
Also, an example being in a short that involves Mrs. Puff trying to cover "Boat Smarts". Being the reckless driver he is, Spongebob causes a crash, and a big accident on the road. Instead of apologizing or feeling bad, he chastises Squidward and Mrs. Puff, claims they forgot their boat smarts, and drives off laughing without punishment.
Incorruptible Pure Pureness: Simply injecting himself with DNA from one of Spongebob's tears was enough to make Plankton pull a Heel-Face Turn, and his heart is so pure that he's immune to jerktonium (a chemical which turns people into jerks.)
Jerkass Ball: Sometimes happens to him in the post-movie seasons, especially in the infamous episode "A Pal For Gary," when he acts like a complete jerk to Gary, even after Gary saved his ungrateful life!
The Kirk: More rational than Patrick; still not as level-headed as Squidward or even Mr. Krabs.
Large Ham: One has to assume that Spongebob's taken drama lessons at some point or another, because overdramatizing is his specialty. He can be more reserved when he wants to be, but it's usually hard for him to go a full episode without lapsing into this at some point.
Lethally Stupid: His relentless stupidity has driven many people (mainly Squidward and Mrs.Puff) borderline, if not completely insane
Made of Iron: Depends on the episode. Spongebob can take a lot of pain, and he just shrugs it off or regenerates.
Nigh-Invulnerability: He seems to be practically impossible to kill at times(he can regrow internal organs). In fact, only when he suffers from a very painful situation such as launching himself onto an island made of spikes or being caught in the demolition of a high tower does he not regenerate near-instantly from his injuries.
Man Child: Boy howdy. Spongebob is said to be an adult who behaves like a child.
Mr. Imagination: He provides the page quote. Another example (though it doesn't spell it out as clearly) is an episode where Spongebob manages to have lots of fun with only a piece of paper Squidward discarded. When Squidward tries, he can't do any of the things with the piece of paper Spongebob did, probably because he has no imagination.
Strong as They Need to Be: Spongebob's strength varies from episode to episode. Some episodes depict him as so weak he couldn't even lift a straw, other depict him lifting a mailbox straight off its hinges. This also applies to his skills in karate; at times he can fight Sandy evenly or even beat her with ease, while at other times he's incompetent to the point where Sandy literally kicks him around like a football.
The Southpaw: He is said to be left-handed or ambidextrous, some episodes you can see him using his left hand to flip patties.
The episode "Demolition Doofus". While his injuring Mrs. Puff was an accident, he takes the level when he shows absolutely no remorse whatsoever for his actions, and makes jokes about her situation instead of apologizing.
Unsympathetic Comedy Protagonist: Zigzagged. His behavior can sometimes go beyond Innocently Insensitive. Sometimes in episodes when he pesters and causes pain to the other characters (Boat Smarts, Good Neighbors, A Pal For Gary, etc), and we're supposed to root for him.
Vague Age: Subverted, in a dream when he got his driver's licence it has the birth date July 12th 1986, meaning Spongebob is 27. Though, that doesn't really explain how he has over 300 employee of the month awards or how he failed the drivers test over one million times.
Why Did It Have To Be Clowns?: Apparently, Spongebob is seriously afraid of clowns, as the only reason he summoned all of Bikini Bottom to his Pineapple in the episode "Rodeo Daze" was to save Sandy from the clowns at the rodeo.
Workaholic: At one point, Mr. Krabs's forcing him to take a vacation nearly caused him to go insane. In "The Splinter," he frantically tries to avoid being sent home early. In "Suds," he drags himself to work, despite being so sick that he can barely stand or keep his eyes open and he's sneezing constantly. Despite insisting that he is okay (punctuated by a loud sneeze,) Mr Krabs sends the guy home so he can rest.
And this exchange from "Graveyard Shift" says it all:
Mr. Krabs: From now on the Krusty Krab is open 24 hours a day. Squidward: What...! Spongebob: Wooow! Now we never have to stop working!
A not-quite-bright starfish and Spongebob's best friend.
Accidental Truth: In the episode "Patrick-Man!", he started attacking patrons at the Krusty Krab, believing that one of them was a supervillain in disguise. When Mr. Krabs is about to throw him out, it turns out that the Dirty Bubble was in fact there in disguise.
Berserk Button: In the first three seasons, Patrick would go a rampage if anything greatly upset him. Examples include being the only person who didn't get a gift from Spongebob on Valentine's Day, Spongebob living with the jellyfish, and being called "Tubby".
Childhood Brain Damage: It is often suggested that Patrick's stupidity is the result of frequent head injuries. In "Squidward the Unfriendly Ghost", Patrick mentions that he knows a lot about head injuries, then spaces out mid sentence. In "Big Pink Loser", Spongebob tries to discourage Patrick from mimicking him by hitting himself with a hammer, to which Patrick responds, "I've been doing this way before I started copying you."
Dangerously Genre Savvy: For an idiot, Patrick may come off as this sometimes, mostly during some of his antagonistic roles.
Disguised in Drag: When he thought a salesman was threatening his life, he, with Spongebob's help, disguised himself as a girl named Patricia. Cue every other male in Bikini Bottom (especially Squidward and Mr. Krabs) falling for him.
Healing Factor: He can regenerate his arms in the unlikely case that they get severed.
Idiot Houdini and Karma Houdini: Often gets away with the things he screws up. The most notable moment is in I'm With Stupid, when he lets Spongebob pretend he was stupid to impress his parents, but then he went too far and actually believed Spongebob really WAS stupid. This causes the sponge to run off in a rage...and Patrick gets away with it.
Man Child: Patrick is an adult and he's almost as childish as Spongebob, if not more.
Manipulative Bastard: This is often how Spongebob goes along in one of his schemes. An example would be the episode in which Squidward accidentally swallowed his reed. Spongebob was told to watch the submarine, and Patrick asked him if he looked after it from the inside as well.
The Millstone: Whenever SpongeBob or anyone has a plan, Patrick is sure to screw it up, or do something stupid to make it worse.
Parental Neglect: In "Rock a Bye Bivalve," he repeatedly refuses to help the baby scallop. Though that in his eyes seems to be a traditional father figure.
Poisonous Friend: For example, Patrick was willing to assault Spongebob's kindly grandmother to keep him from being teased by others.
Another episode called Ghoul Fools showed that Patrick was willing to sacrifice Spongebob because he "lived a full life'. This was actually lampshaded by Lord Poltergeist, who says sarcastically "Great friend you got there."
Vague Age: He's apparently old enough to live on his own and have a job, but is childish to the point where everyone, including himself, refers to him as a kid. However, there are several episodes where Spongebob proves that he is capable of acting his age.
Vocal Evolution: His voice has gotten quite a lot deeper in later episodes. Almost to a creepy extent, he used to sound like a goofball, and now he sounds a tad thuggish.
A cranky perfectionist squid/octopus. Works as a cashier at the Krusty Krab, and is Spongebob and Patrick's neighbor, much to his chagrin.
Accidental Truth: In "Funny Pants," after getting annoyed by Spongebob's non-stop laughing to a joke, Squidward tells him that if he doesn't give it a break, he'll blow out his "laugh box" and never be able to laugh again. In the end, he reveals the trick to Spongebob and laughs over it, finding out the hard way that laugh boxes are real.
All of the Other Reindeer: Hated, avoided, mistreated, and sometimes even assaulted by people in Bikini Bottom, sometimes for no reason.
Ax-Crazy: More specifically in episodes like "Squid's Day Off", "Fools in April" and at the end of "Opposite Day".
Born Unlucky: Nothing ever goes right for him; he is injured, humiliated and/or driven insane almost every episode.
Break the Haughty: Often happens to him. The most subtle example must be the episode in which Squidward tries moving to a town of inhabitants who are just like him...only to end up so bored that he flips out. Naturally, the town haughtily expels him.
Brilliant, but Lazy: It is implied that Squidward would have genuine talent if he wasn't completely sapped of any passion. In "A Breath Of Fresh Squidward" an electric shock alters Squidward's brain and makes him as devoted and high spirited an employee as Spongebob, and actually ruins Spongebob's Employee Of The Month winning streak. Similarly Squidward often goes from a hack to a somewhat plausible musician when in a satisfactory mood.
Burger Fool: You can literally see his dreams of being an artist die in his eyes in each episode.
Iron Butt Monkey: Thankfully, like Spongebob, he's pretty much near indestructible. Being exploded, run over, hit with doors, having his toenail ripped off and being gored multiple times he's still alive.
Camp: Into fancy towel robes, flowers, tea, painting, and playing clarinet, he's definitely got this going for him.
Dirty Coward: When things are looking bad, he'll just run away. Though, it's hard not to sympathize with how messed up the world around him is.
Disproportionate Retribution: In "Fools in April," he gets irritated with SpongeBob pulling April Fools pranks on people and pulls one of his own on him. Of course, SpongeBob's pranks were playful and completely harmless, like putting one ice cube in a customer's drink when said customer asked for a couple, while Squidward's prank was physically painful and just plain cruel. He realizes this only after the damage is done.
He's also become less grouchy and more openly hostile, sometimes even physically attacking Spongebob.
Can you blame the poor guy?
Foil: To SpongeBob in that he can be considered the polar opposite of him.
Forgot Flanders Could Do That: Does occasionally get the chance to display some actual musical or other talent. He was, in fact, initially characterized by Plankton as a "mediocre clarinet player," but has usually been shown as an abysmal one.
Hollywood Atheist: "Just One More Bite" implies that Squidward is either an atheist or a Nay-Theist, with him remarking to Spongebob that he "Has no soul" (a hellish background and laugh pops up behind him when he says that, and he notices, so make of that what you will).
Could also be interpreted in "Club Spongebob", where he mocks Spongebob and Patrick for expecting the answers to all of their problems to "fall right out of the sky" (which they do).
Human Popsicle: During the events of "SB-129", Squidward is locked in the freezer. He thinks someone will notice he's gone and get him out. They do not after 2,000 years, where Squidward travels back to his normal time. So technically, he's over 2,000 years old.
Jerkass Has a Point: Some of his anger towards Spongebob is often understandable for obvious reasons.
Took a Level in Jerkass: In seasons 1-3, Squidward acts like a jerk towards Spongebob and Patrick most of the time, but at some points can be shown to actually care about them. In later seasons he takes the first possible opportunity to Kick The Sponge. Not that it's not justified...sometimes.
Just how sympathetic Squidward is depends on the writer. In the first three seasons, he was just an intolerant grouch; for example, in the first season episode "Naughty Nautical Neighbors," he discreetly ruins Spongebob and Patrick's friendship simply because their talking via bubble-blowing annoyed him. In later seasons, he jumps between intolerant jerk and sympathetic chew toy. It's taken Up to Eleven in "Sponge-Cano!", where he is openly and completely rude, hostile, and disrespectful to everyone and everything he comes in contact with and declares himself to be the most miserable person in Bikini Bottom.
Karma Houdini: In "Grandma's Kisses" he harasses Spongebob for simply being a devoted grandson. "Can You Spare a Dime?" sees him take advantage of Spongebob's hospitality. Then there's "Gullible Pants", in which he fools Spongebob with his gullibility. In all cases, he gets off scot free. This is very surprising when you realize that in several episodes Squidward is punished just for being disagreeable.
Lazy Bum: Common theme of the Krusty Krab episodes is that Squidward often dumps his workload on Spongebob. Since the latter is easily manipulated and very much a workaholic, he takes the extra work without a second thought.
Pet the Dog: Sometimes shows compassion for others. "Pizza Delivery" is the most obvious where a fish crushes SpongeBob's spirit for no good reason and Squidward gets ticked off and shoves the pizza down the offender's throat. Interestingly, episodes like this downplay his Butt Monkey status considerably.
Ungrateful Bastard: In Squidtastic Voyage, when he eagerly screams at Spongebob and Patrick to get out his body without even a thank you for getting the reed out of his throat. This results in a Poor Communication Kills in the end, when he yells "Go!", resulting in Patrick pressing the grow button.
Also on Good Neighbors, Squidward had set up a security alarm in his house as Spongebob and Patrick come in without any problem to give him an apology cake and apologize for unknowingly ruining his Sunday. But Squidward tries to get them kicked out instead of accepting their apology.
"Can You Spare a Dime" is the absolute worst case of this Squidward has ever shown. While initially thankful of Spongebob taking him in from homelessness, Squidward becomes an absolute spoiled brat who refuses to leave and makes Spongebob wait on him hand and foot. And he gets away with it in the end. Almost.
Voluntary Shapeshifting: Into a non-anthro octopus ("Squid's Day Off") and an amorphus liquid ("Suction Cup Symphony").
Ax-Crazy: Even Mr. Krabs is often a step away from this because of his extreme obsession with the money. Watch the episode "Clams".
Badass: Not only was he in the navy, but he also fought an army of skeletons with a swordfish skull! Then he easily defeated a group of destructive ghosts with a freaking mop!
Bad Boss: He has become this, not caring about his employees or his customers and willing to do anything to get a buck, even poison them. He still showed shades of this in the pre-movie seasons; for example, in "Squid on Strike," he decides to start charging Spongebob and Squidward for anything and everything they do that doesn't involve working, including breathing, talking, and even existing.
Benevolent Boss: At least toward Spongebob, less so in later seasons, but Spongebob still sees him as one.
Big Bad: In later seasons. According to Stephen Hillenburg, Mr. Krabs and Plankton are both the main antagonists.
Blue and Orange Morality: Several episodes have shown his selfishness and greed may, in part, be natural for crabs, as apparently every crab's goal in life is to make a million dollars and they regularly hold a competition to decide which of them is the cheapest.
Easily Forgiven: No matter how badly he treats SpongeBob or how heinous his actions may be, he will always be back in SpongeBob's good graces by the end of the episode. A particularly noticeable example is in "The Cent of Money," in which he uses (and abuses) Gary to steal money and loose change from all of Bikini Bottom, completely uncaring that attracting money causes Gary great discomfort.
Hair-Trigger Temper: When it comes to money. Seriously you can hurt and kill his employees and he won't care, but so much as touch his money and he will flip the entire world around trying to hurt you.
It Amused Me: In "Wet Painters," Mr. Krabs convinces Spongebob and Patrick to paint the inside of his house, but states that the paint in question is permanent and if they get even a single drop on anything but the walls, he will chop their butts off and mount them over the fireplace. They accidentally get it on his first dollar, and Mr. Krabs simply licks the paint off and reveals that the paint is actually saliva-soluable. When he tells them that he told them as such just to mess with them, Sponge and Pat are not happy and immediately leave in disgust.
Mr. Krabs is a jerkass more and more every season. He is arguable the best jerkass in the show.
Mr. Krabs was initially a quirky but rather fair natured boss character. He just liked money ''a bit'' too much. His greed was often played for laughs, and he had redeeming qualities, such as genuine care for his daughter Pearl, and for Spongebob. Now at times he's just a total jerk to anything without a currency value. There's still some episodes that show him as a good guy though.
Karma Houdini: In post-movie seasons, he is essentially the living, breathing incarnate of this trope, considering that he somehow gets away scot-free with anything he does nowadays (ranging from theft to poisoning his customers to even driving people to suicide), sometimes leaving someone to take the blame/pay the price. There are even times near the end of some episodes when it looks like Krabs is about to receive his comeuppance (or in rare cases, actually does), but something happens at the end that puts the situation in Krabs's favor, if not lets him escape punishment entirely.
However, he still doesn't get away with everything. For example, at the end of "The Patty Caper," just as his plan to frame Spongebob for the theft of the Krabby Patty secret ingredient is about to succeed, he reveals the ingredient in his hand and confesses to stealing it himself, and is forced by the judge to give out free Krabby Patties for a whole day, while strapped to the chair and being Forced to Watch by the cops. Might not seem like an actual punishment, but when you're as greedy and miserly as Mr. Krabs...
Knight Templar: His occasional treatment of Plankton leans towards this, early on he was merely defending his business from his schemes, now he seems to take offense even when his rival is making legitimate profits or merely isn't miserable.
MONEY FETISH: His defining character trait. He frequently to ridiculous levels, to the point of taking money-baths, getting into a fight with Squidward over a dime, stalking Spongebob for a penny, and almost losing Spongebob forever in exchange for some pocket change (sixty-two cents to be exact).
Mr. Vice Guy: When the show started out, he was a decent guy, but a bit greedy.
Badass Bookworm: Easily the most intelligent in the main cast, but often shown to be as physically strong as Larry the Lobster. Also likes life-threatening stunts.
Berserk Button: Never ever insult anything/anyone from Texas, or even the state itself. You will regret it, as Spongebob and Patrick faced the serious consequences.
Closer to Earth: Flip flops with this. While she is far more intelligent than most of the cast, she is occasionally shown to have a very rowdy and abrasive temperment when pushed. She is also sometimes more aware of her position in this trope than she really is. Granted as the rest of the cast became Flanderized more and more, her own flaws became less significant.
Competition Freak: Sandy is used to being the best at multiple talents and sports, so gets rather aggressive with when challenged.
Cute Bruiser: She is clearly Bikini Bottom's strongest resident, occassionally challenging massive, heavily muscled fish and Larry the Lobster to weightlifting challenges.
Demoted to Extra: Inverted: She and Gary are more common in merchandise than the show.
Noble Bigot: In "Pressure," she repeatedly bragged that land creatures are better than sea creatures, with Spongebob, Patrick, Squidward, and Mr. Krabs thinking the opposite. However, after their attempts at proving it put both sides in mortal danger, they grow out of it.
Only Sane Woman: Not as much as Squidward, but she's still fairly level-headed. This is the reason why Squidward has no problem with her.
Slapstick Knows no Gender: Not as much as the others but Sandy suffers some physical damage at times, such as being mauled by a gorilla, having her fur torn off by Spongebob and Patrick, being plagued with fleas, being hit by a car off of a mountain and so on.
In "Pressure," she repeatedly stated that land creatures are better than sea creatures and went so far as to almost drown herself in an attempt to prove it.
Then there's "Sandy, SpongeBob, and the Worm," where she was firmly convinced that, being "Texas tough," she could easily handle the Alaskan Bullworm, repeatedly dismissing and even mocking SpongeBob's warnings. When she finally reaches it and finds out that the Alaskan Bullworm is indeed as big and dangerous as everyone said, she runs in fear, and only admits she was right after SpongeBob nagged her into doing so.
Her occasional ego and temperament can provoke some unfortunate situations in the show (eg. ''Pressure), that said, she is arguably the one recurring character that hasn't had her flaws Flanderized over her redeeming aspects.
Women Are Wiser: Usually played straight to a tee, though she has occasional lapses in judgement Spongebob plays The Straight Man towards, especially in early seasons.
Sheldon James Plankton
Voiced by: Doug Lawrence
Krabs' business rival and arch-enemy. Is always after the formula for the Krabby Patty, the burger that SpongeBob fries up to the customers. Barring that, he ultimately aims for crushing all of Bikini Bottom beneath his feet.
Affably Evil: He is no less pleasant than his rival can be anyway.
Can't Get Away with Nuthin' : Not just with his evil plans. A rather discomforting example would be "One Coarse Meal", where Plankton is punished for trying to exact justifiable revenge on Mr. Krabs, who in turn got off scot-free after tormenting Plankton for several days.
However, Plankton does partially get away in "Someone's in the Kitchen with Sandy". After yet another failed attempt to steal a Krabby Patty, he is locked in a jar of spicy mustard. Then the police show up and - instead of arresting Plankton for stealing Sandy's pelt - they arrest SANDY for public nudity.
Determinator: Much much more so in earlier episodes, but there are some later episodes in which he's given up.
Ditzy Genius: He may be a scientist and have all sorts of gadgets, but is incompetent overall. For example, he believes that baby powder is made from actual babies in "Goo Goo Gas," and in "Komputer Overload," he has to be reminded to blink.
The Dog Bites Back: In "One Coarse Meal", when he nearly kills himself after being frightened by Mr. Krabs in disguise as Pearl from his fear of whales for 17 straight days, he finds out about Mr. Krabs's fear of mimes and starts scaring him with that. It doesn't last long, though.
In "The Krabby Kronicle," he doesn't invade people's privacy for a newspaper gossip and shows disgust at Krabs' greed. Quoted by him "And I thought I was evil!"
In "Squirrel Records," Sandy comes to him asking for raw chum in order to break a world record. Plankton is actually reluctant to give it to her despite freely admitting to being an "evil, heartless mastermind," because, as he puts it, "no one can eat raw chum and survive!"
Hair-Trigger Temper: Much more so in earlier episodes, he's calmed down a tad in later episodes.
Harmless Villain/Not-So-Harmless Villain: Played with, his only interest is stealing Krabs' secret formula. However depending on his overzeal, he is willing to brainwash, potentially murder and generally cause a lot of collateral damage in his attempts to do so. In other episodes that aired after the movie, he even settles for just competing with Krabs legitimately.
Last Name Basis: Though in his case, he considers Sheldon an Embarrassing First Name. Unlike Mr. Krabs, he's simply called Plankton instead of Mr. Plankton (sans one episode where he sees what it's like if they switch places).
Took a Level in Badass: After stint of Villain Decay Plankton returned to his threatening and menacing self by Season 7 and became a much more competent villain. Particulary in episodes "Frozen Face-Off", "Spongebob's Last Stand" and "One Coarse Meal'. In "Frozen Face-Off" he organized race as a distraction just so he could steal Krabby Patty formula without trouble and to throw off the suspicion he placed his robot doppelganger to participate in the race and it took all the main characters to stop his Evil Plan. In "Spongebob's Last Stand" where he built a super highway, which directly led to Chum Bucket, and it drove away all jellyfish from their fields and took over town and almost all of Bikini Bottom's population supported him until the jellyfish attacked them in revenge for their home's destruction. It was so bad that Mr. Krabs was going to give him the secret formula willingly. This and "Frozen Face-Off" are more dramatic and action packed episodes of the series. Even in "One Coarse Meal', where he was Driven to Suicide due to Krabs masquerading as Pearl and scaring him, Plankton was very effective villain. He drops a powerful explosive the size of a TV remote on the Krusty Krab's roof; he is said to build a transmutator (a machine with the power to make an element in nature into another element, like iron into gold, fire into air, etc.); and a robotic bomb-shaped object that is actually a disguised, robotic, telescopic claw that can crush a sea creature. And during the end of episode, Plankton uses mime to scare Mr. Krabs, who is very afraid of mimes, as the revenge for Mr. Krabs scaring him and driving him to suicide and from looks of it, Mr. Krabs' fear of mimes is bigger than Plankton's fear of whales, since Plankton managed to remain rational while being scared by whales, while Mr. Krabs was completely irrational.
Tragic Villain: For some, he could be seen like this. It is known that as a child, he was bullied and his only friend was Mr. Krabs. Now he is evil and despises the society, not only because of this, also for a dispute with Mr. Krabs for poisoning the old man Jenkins.
Villainous Breakdown: He has one in The SpongeBobSquare Pants Movie. After his helmets have been proven to be defeated by the Power of Rock, he tried to desperately beg his computer wife Karen to do something about SpongeBob. However, she was being carried off by the crowd and was too far away to hear her husband. As one final act of desperation to keep his control over the townspeople, he tried to command the brainwashed King Neptune to kill SpongeBob. Unfortunately for him, the helmet on Neptune's head was also destroyed, and he was freed from his mind control. Plankton then tried to escape through the front doors, only to be paved down by the freed Bikini Bottomites. He's later arrested, and he threatens to murder everyone once he gets out of prison.
Villain Protagonist: Only in some episodes, showing his attempts to want to steal the Krabby Patty formula.
Vocal Dissonance: He has quite a deep, booming voice, in contrast to his miniscule size.
Vocal Evolution: Starting in the movie, he would develop a high-pitched scream.
0% Approval Rating: Has been referred to as the "most hated thing/creature in Bikini Bottom" on more than one occasion.
Voiced by: Jill Talley
Plankton's business computer and robotic spouse. Being blessed with a complex sentient programming, Karen is well aware of her "husband's" stupidity and is very verbal about it as well.
A.I. Is a Crapshoot: Seems more competent and intelligent than Plankton, but also has the personality of a nagging housewife, and thus is usually more preoccupied in nagging at her husband's failures or whining for affection.
Robotic Spouse: Yes and no. Yes, Karen is a robot (okay, she's technically an extremely sarcastic computer...). But no, it's never fully explained how/when she was built, or when she and Plankton were married (if they're even married). Plankton may have originally built her to be the perfect wife or just a generic computer, but since A.I. Is a Crapshoot, her AI may have evolved into the snarky computer you see today.
Cats Are Mean: Under the show's theory of snails existing as an Expy for cats. Subverted for the most part, though he has his occasional Jerkass moments like most of the cast (Dumped shows he can be a rather fickle bastard).
Knight of Cerebus: She briefly becomes one in the Season 8 episode Demolition Doofus. She entered SpongeBob into a demolition derby and hoped that he would die in it since he was the one who caused her to puncture her inflation sac thanks to his crazy driving. She later tries to kill him herself by entering into the demolition derby using a massive monster truck. This episode is considered her darkest role by many fans.
Nervous Wreck: She's very neurotic, although it's usually justified.
Granted, this was back in the second season where he was still a nice guy and before he became a Jerkass.
Out-of-Character Moment: In the infamous Demolition Doofus, she is driven insane after one of SpongeBob's accidents causes her to deflate. She actually tries to get SpongeBob killed in a demolition derby. Thankfully, she was turned back to normal at the end.
Even Evil Has Standards: Not only he looked surprised that Mr. Krabs was willing to sell his soul so eagerly and took the whole ordeal lightly. But he looked dumbfounded that Mr. Krabs sold his soul to other ghosts, monsters, and demons. Plus to Spongebob because he was low on payday.
Stylistic Suck: He looks like a cheap puppet that's falling apart (and his strings are always visible). His facial expressions never really change (although you can tell when he's annoyed by his voice).
Not-So-Harmless Villain: A minor villain in the normal series, but a Bad Future where he won proved he was actually able to take over the world and turn it into a dictatorship where everyone was enslaved to his will.
Squidward's rival from high school. Squilliam is essentially everything Squidward dreamed of being. Whereas Squidward is a middle-class jackass stuck in a dead end job and considered a joke by everyone except SpongeBob and Patrick, Squilliam is a successful, filthy stinking rich jackass beloved by all. Also, unlike Squidward (who has had a few Pet the Dog moments), he appears to have no redeeming qualities whatsoever. He loves rubbing his success in Squidward's face.
Villainous Breakdown: At the end of "Band Geeks", he has one. Seeing Squidward completely succeed in an absolutely epic way causes him to have a heart attack!. Has another one at the end of "House Fancy" were Squidward's house being declared even fancier than his leaves Squilliam laying on the ground crying his eyes out.
The Bully: He threatens to kick Spongebob's butt the minute he lays eyes on him.
Jerkass: He has no reason to antagonize Spongebob, but does so anyway.
Debut: "Neptune's Spatula"
Jerkass Gods: He was slightly nicer in his first appearance, though.
Kevin the Sea Cucumber
Debute: I'm Your Biggest Fanatic
For the Evulz: He picks on and belittles Spongebob and then tries to drive him off a cliff for no apparent reason behind his own amusement. And later it's implied that he's done this to all of his "biggest fans".
Karmic Mutilation: He doesn't die, but he does get the fronds on his head torn off at the end of his episode. It should be Body Horror, but he deserved it for the massive jerk he was being.
Know-Nothing Know-It-All: The end of his first appearance reveals that he actually knows nothing about jellyfish, and the only reason he got into jellyfishing in the first place was because of the merchandise.
The ruler of the sea, whose crown is his prize possession and holds his symbol of authority over all his undersea kingdom. It should be noted that he is not the same King Neptune that appears in the series, and is exclusive to the movie.
Jerkass Gods: More so than his series counterpart - he was going to imprison someone who touched his crown for 20 years. The kicker? Said person was the royal crown polisher.
Jerk with a Heart of Gold: At the end of the movie, King Neptune gets an aesop on how important it is to have love and compassion when you're in a position of leadership. He also apologizes to Mr. Krabs for freezing him and praises SpongeBob.
Not Quite Dead: The Cyclops stepping on him does not kill him, as he returns riding on "bigger boot". However, he's not seen again after colliding with something and falling off the back of David Hasselhoff.
Saying Too Much: Lampshaded when he accidentally slips that Plankton stole Neptune's crown.
A friendly mermaid who does her best to assist SpongeBob and Patrick in their quest to Shell City. She disproves of her father's method of ruling with an iron fist, and wishes he would use a little love and compassion. She is also the target of Patrick's affections.
Humans Are Cthulhu: To the audience, he's just a guy in an old-fashioned diving suit. To the characters, he's an incomprehensible monster defined by his unnaturalness and willingness to kill sea creatures..
Knight of Cerebus: He only appears for a few minutes, but those minutes are probably the darkest minutes in the whole movie, maybe even the series.
Laser-Guided Karma: He ends up being attacked by the sea creatures he turned into marine gifts and suntries.
Vile Villain, Saccharine Show: Remember how Dennis came close to killing Spongebob and Patrick? This guy actually succeeds. Sure, they get better, but even so...
King Neptune's Squire
Voiced by: Carlos Alazraqui
King Neptune's Squire, who accompanies Neptune pretty much wherever he goes, and must obey his every command.