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[[folder:James "Jimmy" Isaac Neutron]]
[[caption-width-right:153:"Gotta blast!"]]
->Voiced by: Creator/DebiDerryberry

The main protagonist. He is a boy with a stunning IQ and a love for science. From Hypercubes to Hypnorays, Jimmy can whip up the most amazing inventions. However, things have a way of going awry, and more often than not, Jimmy has to save the day from himself. But with friends, family, and a secret lab, there's no problem this boy genius can't handle. Right?
* {{Adorkable}}: He's a nerdy protagonist. This was inevitable.
* AesopAmnesia: At least half of the episode plots wouldn't happen if Jimmy would remember how often his inventions backfired.
* AnimeHair: Lampshaded consistently.
* AntiHero: Jimmy is a complex character, often prone to arrogance and mischief, although the good side of his personality usually outweighs the bad one. That being said...:
** In "See Jimmy Run" he comes up with a pair of super-fast shoes in order to beat Cindy at a relay race. When his efforts fail, he resorts to take revenge on her by putting her in all sorts of misfortune. In other words, [[WhatTheHellHero Jimmy punishes Cindy for being better than him at something]]. He does get his [[LaserGuidedKarma comeuppance]] at the end though.
*** It's not exactly uncommon in the show to see similar scenarios play out but the big difference is that here we never see Jimmy actually ''learning'' from his mistake.
** In "Brobot" he invents a little robotic boy to fill in for a brother he always wanted to have. But once Brobot starts to overshadow Jimmy, all the while admiring him as his big brother and [[IJustWantToHaveFriends best friend]], Jimmy just gets rid of him. And while Brobot definitely could have done worse than get a pair of robotic parents and be sent to the Moon, this episode is definitely at the top of the list when it comes to Jimmy's most JerkAss appearances in the show.
** "Love Potion 976/J" features Jimmy falling for Cindy as a result of being accidentally exposed to the titular love potion and he invites her over to his lab to ask her to be his Valentine. He does snap out of it once he realizes what happened and promptly tosses Cindy out of the lab. Considering that we know for a fact that Jimmy does indeed have a crush on Cindy anyway (although he himself doesn't seem to quite realize that until the very few last episodes of the show, as opposed to her who secretly loves him from the start but just won't admit it), he gives her quite a rough treatment (at one point even calling her gross which definitely goes way beyond the standards of these two's everyday bickering) and we may assume that for all Cindy knew, he was just cruelly playing with her feelings.
* BelligerentSexualTension: With Cindy.
* BerserkButton: Do NOT give Jimmy an F. [[WesternAnimation/TheFairlyOddParents Denzel Crocker]] in the [[CrossOver Jimmy Timmy Power Hour]] learns this the hard way.
* BewareTheNiceOnes: While Jimmy's hardly a stoic, it takes a lot of effort for his close friends to ''really'' piss him off. One of the few episodes where that happens is "Carl Wheezer: Boy Genius", in which Carl's taking on Jimmy's genius identity just to impress a girl pushes Jimmy to the absolute limits of sanity. Considering that Carl is more than willing to abuse his "dim-witted assistant", nobody can blame Jimmy for wanting to blow his friend's cover at any given time.
* BigDamnHeroes: ALL THE TIME. Often Lampshaded, in fact.
* BigNo: Whenever Jimmy comes to any shocking realization, you can bet the whole of Retroville will know about it instantenously.
** In ''The Tomorrow Boys'', after learning he gets married to [[spoiler: Cindy]]. In a bit of LeaningOnTheFourthWall, the scream cuts to a commercial. When the show comes back on, Sheen comments that he had been screaming for four minutes straight.
** Another Cindy-related moment is when he finally succeeded in asking Cindy on a date, only then he ralized what he'd done
--->'''Jimmy''': *jumping and pumping fist to the air* "I did it! She likes me! She's gonna go out with me! I made a date with Cindy!" *beat* [[BigNo "NOOOOOOOOOOOOOOOOOO!"]] [[SkywardScream *shot of him from up, and then zooms out to Retroville and Earth*]]
* BlackSheep: In one episode, most of the Neutron extended family views him as such, correctly pointing out that, while Jimmy may have saved the day quite often, more often than not, it was one of his inventions that [[NiceJobBreakingItHero caused the problem in the first place]].
* BrilliantButLazy: Why do something as simple as neatly put away your piles of pants when you can implant chips in them that do it for you? Carl and Sheen call him out on this, though.
* BunglingInventor: While he's undoubtedly a genius, the plots of most episodes are kicked off when his inventions go haywire.
* ButtMonkey: His inventions usually cause troubles. And when it doesn't come to his inventions, he's picked on by those left and right.
* CassandraTruth: In the episode, "The Eggpire Strikes Back", no one believes Jimmy when he says that the Yolkians, the villains from the pilot film, are still just as evil as ever, until Poultra is bearing down on him.
* CatchPhrase: Originally "Gotta blast!" "Think, think, THINK!" and "Brain blast!". The show eased off on these as it went on, eventually getting rid of them entirely. (One exception is "And now, my latest invention, the (insert plot-related-device here!)", which stayed for most of the series' run.)
* ChildProdigy: A preteen genius who has an IQ of 210.
* CrazyPrepared: His watch, whose powers depend mainly on the plot. Can include lasers, freeze rays, magno-rays, GPS, tracking devices…you name it, there's probably a gadget for it tucked away in there.
* DeadpanSnarker:
--> '''Jimmy''': *science babble about a spider*
--> '''Sheen''': Fascinating! Can you make it do the hokey pokey?
--> '''Jimmy''': Sheen, go home.
* {{Expy}}: He's very similar to [[WesternAnimation/DextersLaboratory Dexter]], being a diminiuitive and easily frustrated boy genius who has his own laboratory which leads to hillarious mishaps. Ones wonders what it would have been like if he had to deal with Dee Dee.
* FatalFlaw: Jimmy's greatest flaws are a combo of {{Pride}} and his lack of common sense; in fact, many of the conflicts in the show are born out of this.
* FutureLoser: In the 'BadFuture' of ''The Tomorrow Boys'', Future!Jimmy is a slack-jawed loser, wanted by the evil dictator Libby, with a five-o'clock shadow and [[spoiler: Cindy]] as a wife. Current!Jimmy is [[FutureMeScaresMe less than impressed]].
* GadgeteerGenius: He is only a kid, but he has already surpassed any known scientist in capablity. Each episode focuses on one of his invention although his inventions usually fall prey to FlowersForAlgernonSyndrome.
* GetBackToTheFuture: Jimmy's dad screwed up with one of his inventions, leaving him, Carl and Sheen in the past.
* HeCleansUpNicely:
** When Jimmy shows up in a tux for Jet Fusion's wedding to Beautiful Gorgeous in ''My Big Fat Spy Wedding'', Cindy promptly gets little hearts in her eyes.
--> '''Cindy''': "So Neutron's the best man? Yeah, more like the best NERD! I bet he'll look like a total…" (''Jimmy shows up outside the church in a tux. Cue fade to pink background, [[WingdingEyes eye-hearts]] and hair patting'') "…HUNKMUFFIN."
** During ''Love Potion #976-J'', when Jimmy cleans up for his date with Cindy. Said almost word-for-word by Cindy.
* HeightAngst: He's shorter that the main casts (and Retroville kids his age in general), and he's not happy when someone mentions or ridicule his short stature.
* HellYesMoment: Often. Especially when he's given up all hope... and then his friends forgive him for being arrogant/apologize for being stupid/come back to save him.
* IdiotHero: For a genius, Jimmy sure makes a lot of utterly stupid decisions. In fact, most of the conflict that goes on in this show is the result of Jimmy making a questionable judgment call in the first place regarding his experiments. But then again, Jimmy's lack of common sense is arguably one of the main points of the series. He may be a "genius," but he's still a child.
* ImYourWorstNightmare: His quote when first introducing himself and the others as N-Men.
-->'''Jimmy''': "Who am I? I'm your worst nightmare."
-->'''Cindy''': "By the way Neutron, who said you can issue a corny battle cry and where do you come up with N-Men?"
* InsufferableGenius: At times, but often more pronounced when Cindy's around.
* IntelligenceEqualsIsolation: Sometimes intelligence isolates him, often he sets the (horrible) events of the plot in motion causing him to be isolated, sometimes the characters realize they need his intellect &/or like him more than they let on, and sometimes he's just an insufferable genius. He actually purposely made himself stupid in one episode to end his misery, but the machines accidently set his intelligence so low he became a complete moron.
* KidHero: Jimmy is only 10.
* LittleProfessorDialogue: Justified partially in that he does actually have an IQ of ''210''.
* NerdsAreInnocent: He's a child prodigy who loves and excels at science...and still believes in cooties.
* NiceJobBreakingItHero: 99 out of 100 times, his inventions end up causing problems for everyone in Retroville, leading him to fix what he broke. As revealed in one episode, the majority of the Neutron extended family views him as the BlackSheep as a result. However, this trope is used less and less in later episodes.
* PetsHomageName: Jimmy designed and built his robot dog and named him Goddard in honor of rocket science physicist and inventor Robert Goddard. Especially apt when, in his first animated feature film, Jimmy is able to ride upon Goddard like a space bike.
* ProperlyParanoid: He knew better than to trust the Yolkians in "The Eggpire Strikes Back."
* PuppyLove: With Cindy.
* RidiculouslySuccessfulFutureSelf: In the 'good future' of ''The Tomorrow Boys'', Jimmy is the first person to ever win the Nobel Prize in bulk.
* RivalTurnedEvil: In ''The N-Men''...
* ScienceHero: He embodies this trope for kids shows, along with [[WesternAnimation/DextersLaboratory Dexter]].
* SesquipedalianLoquaciousness: A frequent user and abuser.
* SlapSlapKiss: With Cindy. All the time.
* TheSmartGuy: Duh.
* TookALevelInDumbass: For someone so smart he tends to let his overconfidence and arrogance get the best of him quite a few times. When he accidentally drained his brain too much in ''Normal Boy''.
* TVGenius: He is an elementary school student who is not only excessively prone to TechnoBabble and SesquipedalianLoquaciousness, but has invented time travel, faster-than-light warp engines, and the best candy in the history of all existence and everything. Also, he has a giant head.
* UnsympatheticComedyProtagonist
* YankTheDogsChain: One of Jimmy's signature flaws. When some of his inventions start off good, then backfire on him right afterwards.

[[folder:Carlton "Carl" Ulysses Wheezer]]
[[caption-width-right:210:"You look like a couple of intelligent young men!" [softreturn] "Nuh uh, it's just the glasses."]]
->Voiced by: RobPaulsen

Jimmy's shy, asthmatic best friend who has an unhealthy obsession with llamas and Jimmy's mom.
%%* {{Adorkable}}
* BigEater: You'd think having so many allergies would limit this, but no. Carl can chow down with the best of 'em and has a stomach of steel. Occasionally overlaps with ExtremeOmnivore for laughs:
-->'''Carl:''' I don't eat newspapers! '''(Beat)''' Well, I'm trying to quit.
* ButtMonkey: He's the Guinea pig to all of Jimmy's experiments.
* CowardlySidekick: To Jimmy.
%%** CowardlyLion
* CatchPhrase: "My scapula..."
* {{Fartillery}}: Gets this in "The N-Men" (see {{Gasshole}} below).
* FatBestFriend: Generally a straight mixture of a Type C (though not as big of a {{Cloudcuckoolander}} as Sheen) and a Type B (being shy). Which one dominates depends on the episode.
* {{Gasshole}}: He has burped more than anyone else on the show (except for Jimmy's dad). In "The N-Men", he gets hit by some cosmic radiation that turns him into "Belch Boy", allowing him to unleash [[MakeMeWannaShout sonic blast]] burps by drinking seltzer or shaking himself really hard.
* GreenEyedMonster: Implied quite heavily in "I Dream of Jimmy" and "Carl Wheezer, Boy Genius" that [[IJustWantToBeYou he'd really like to have Jimmy's life.]]
%%* TheHeart
* HollywoodToneDeaf: His most attempts at singing something.
* {{Hypocrite}}: Out of the entire trio he is the one most outspoken about how boys should not take interest in girls even though he has hots for them just as often as Jimmy and Sheen do.
* ItRunsInTheFamily: His allergies. Turns out his mother and father have various allergies too.
* JerkassBall: Carl takes it in "Carl Wheezer, Boy Genius", which starts out as a standard "I lied to my pen pal" farce, then quickly escalates as we learn Carl lied about having ''Jimmy's'' life. It goes downhill as Carl not only has to masquerade as a boy genius, but he forces Jimmy to be his "lowly assistant", berating and constantly screaming at him for all ''his'' mistakes. Even by the end, when Jimmy has saved his life at least three times, Carl is ''still'' screaming at him... and projecting his own insecurities onto Jimmy to boot. Naturally, the whole thing made Jimmy incredibly furious.
* LikesOlderWomen: Carl has a crush on Jimmy's mom since ''Love Potion #976-J''. He's also attracted to the class's teacher, Miss Fowl, who's in her fifties. At ''least''.
* LooseLips: Sheen helps him a lot with this one. They're often the ones to reveal the secret plan to the enemy, generally via SuspiciouslySpecificDenial.
* MinorInjuryOverreaction: Even the smallest tap on any part of his body will cause him great physical pain. He pretty much inherits this from the rest of his family as well.
* NerdGlasses: Wears a pair of big glasses.
* NerdsAreInnocent: He's a nerdy boy who's shy, sensitive, and often serves (or at least tries to) as the moral compass in his group of friends.
* NerdyInhaler: Carl uses an inhaler very frequently and is also allergic to almost everything.
* OwMyBodyPart: A weirdly specific example--he seems to have a really tender scapula.
* PrecociousCrush: On Jimmy's mom.
* ShrinkingViolet: He's generally shy and nervous.
* SicklyNeuroticGeek: What else can you expect with a surname like 'Wheezer'?
* StalkerWithACrush: To Jimmy's mom.
* VoiceChangeling: In The Incredible Shrinking Town, It was said he coould do this from a ventriloquism lesson. The result was awesome. He was capable of impersonating Cindy's Mom's and Zix's voice perfectly.
* YouthfulFreckles: Has many freckles that match his red hair.

[[folder:Sheen Juarrera Estevez]]
[[caption-width-right:300:"Back, or I will slay you with my medulla oblongata!"]]
->Voiced by: Jeffrey Garcia

Jimmy's hyperactive other best friend who is obsessed with the comic book superhero Ultra Lord.
* AccentAdaptation: In the Latin American dub, he speaks with a Japanese accent, possibly because the translators thought that he's Japanese-American, instead of Hispanic, and his name should be pronounced "Shin".
%%* {{Adorkable}}
* BadassBoast: In ''Sheen's Brain''.
-->I control the wind, and I shall rain fire down from the heavens! Goodbye Sheen the overlord. [[AGodAmI Hello Sheen the God!]]
* BerserkButton: Do NOT call Ultra-Lord a doll. Or mock Ultra-Lord in any way.
* BetaCouple: With his sweet princess, Libby.
* BreakoutCharacter: Gets his own SpinOff, ''WesternAnimation/PlanetSheen''.
* ButtMonkey: He suffers a fair amount of physical abuse. He is also sometimes used to test Jimmy's experiments, but he actually enjoys this.
* {{Cloudcuckoolander}}: In a minor but interesting play off of the idiot sidekick shtick. Sheen isn't exactly stupid (at least before Flanderization set in); he's just very, very scatterbrained.
* TheDitz: His IQ is 32.
* DrunkWithPower: When his intelligence is increased in ''Sheen's Brain''.
* EarlyInstallmentWeirdness: He mentions a sister in "I Dream of Jimmy" but WordOfGod has said since to disregard it. Canonically, Sheen is an only child who lives with his father and grandmother (at least until ''WesternAnimation/PlanetSheen'').
* ExtravertedNerd: An eccentric comic book-loving nerd.
* GeniusDitz: He has enough smarts to write a website, at least. Granted, said website is filled with inaccuracies about [[ShowWithinAShow Ultra-Lord]](like stating he was the father of the country), but writing and launching a website is still no mean feat in and of itself.
* GoofyPrintUnderwear: Limited Edition Ultra Lord Underwear! Only available in Japan!
* HollywoodToneDeaf: His singing is so bad, it actually puts the music-hating Twonkies to sleep.
* {{Keet}}: He's very energetic.
* LoonyFan: He's obsessed with cartoon superhero Ultra Lord.
* LooseLips: See above.
* MetaGuy: A lot of his {{Non Sequitur}}s are lampshades, especially as the show went on. A RunningGag in the later seasons has him predict that an adventure is imminent before any of the other characters even get to that point (so much so that him saying [[SharePhrase "to the lab!"]] early becomes kind of a catchphrase). In ''Stranded,'' for example, he can tell it just from the fact that Jimmy and Cindy are arguing:
--> '''Sheen:''' "Just a little longer, Carl. Our adventure should start at any minute."
--> '''Carl:''' "What adventure?"
--> '''Sheen:''' "You'll see..."
* MissingMom: According to [[WordOfGod the creators]], [[TearJerker she died when Sheen was little]].
* PluckyComicRelief: He serves as the funny sidekick on the show.
* PuppyLove: With Libby.
* TheSlacker: Watches Ultra-Lord while trying to do his homework
* TheWatson: Has his moments.
* WideEyedIdealist: He believed that there was goodness in Tee and was proven right.

[[folder:Cynthia "Cindy" Aurora Vortex]]
[[caption-width-right:210:"Listen, Neutron, I'm a girl with looks and brains and big plans for my future and they ''don't'' include living in a world ruled by pants!"]]
->Voiced by: Carolyn Lawrence

Jimmy's rival who has a crush on him. Not that she'll admit it.
* AbusiveParents: Hinted at throughout the show, although the full picture is mostly ambiguous. While it's certain that Mrs. Vortex is a rather strict parent (not much is known about her husband, him being TheVoiceless and all) who probably played the key role in developing Cindy's vast ambitions as well as had her enroll in an overwhelming number of extracurricular activities, she genuinely cares for her daughter and supports her at every turn, most notably shown in "Win, Loose, Kaboom" where she is [[MamaBear the first to suggest that the Retroville parents start working on getting their children back instead of just standing and watching]].
** Both [[WesternAnimation/JimmyNeutronBoyGenius the movie]] and [[VideoGame/JimmyNeutronBoyGenius its video game adaptation]] confirm that the Vortex family members genuinely love each other.
* AcademicAlphaBitch: Jimmy took her "smartest person in Retroville" title when he moved into the house across the street from her, whereupon Cindy, now second runner up, began a rivalry with him.
* AcademicAthlete: The smartest student after Jimmy and knows karate enough to kick asses.
* ActionGirl: Cindy practices karate.
* BadassBookworm: Other than being smart, Cindy is more athletic than Jimmy and practices a lot of martial arts sports.
* BareYourMidriff: As Special Girl.
* BelligerentSexualTension: With Jimmy.
* CannotSpitItOut: Cindy's extremely cautious when it comes to saying things she might regret afterwards so she usually avoids it when she can. And when she knows she should apologize to Jimmy or otherwise acknowledge his intellect or skill, it's bound to come out after a prolonged period of awkward silence or "Neutron, I hate to say it but...". Obviously applies to revealing her true feelings about him as well.
* ClingyJealousGirl: She doesn't like seeing Jimmy showing interest in other girls.
* TheCorruptible: Has some experience with that.
** In "The Egg-Pire Strikes Back" she tells King Goobot how to get inside Jimmy's lab after learning it from Carl and Sheen. Partly subverted since for all she knows they just want to help her in being able to compete with Jimmy on an equal footing by means of building a lab of her own. While she is dumb to trust the Yolkians, so is everybody else in town except Jimmy, and when she realizes that her actions put the whole Retroville in danger she is first to call on others to believe Jimmy and help him bring down Poultra.
** "King of Mars" has her defecting from the gang to join Eustace Strych. Again, subverted because the only reason why she does it (and the very argument Eustace uses to convince her) is to make Jimmy finally take notice of her. That is also why she is EasilyForgiven later on.
* DeadpanSnarker: Often prone to snide remarks.
* DefrostingIceQueen: Towards Jimmy over the course of the show, as her affection towards him becomes more evident.
* DependingOnTheWriter: Somewhat averted since there doesn't seem to be any direct link between a particular writer and the way Cindy is portrayed. Then again, you can't help but wonder how she is able to be a mean-spirited bitch in one episode, a genuine if respectable rival to Jimmy in the next and a totally likeable character in the third, only for the cycle to start all over again. Her bad side shines through much more often early in the series but it's still there come the very end. In fact, the inconsistency gets so striking that it appears like some episodes were aired out of chronological order.
* {{Expy}}: Of [[WesternAnimation/HeyArnold Helga Pataki]]. Both of these tomboyish blonde lasses each harbor crushes on the main protagonist but act villainous and bully them whenever they're present, to hide it.
* GirlishPigtails: In the movie.
* GoofyPrintUnderwear: Polka dot panties.
* GreenEyedMonster: At least part of her problem with Jimmy stems from this. In The Movie, she says that before Jimmy came along, ''she'' was the smartest kid in school. It's a given that she didn't appreciate being knocked down to number two.
* HintDropping: Unfortunately, Jimmy seems to permanently be holding the IdiotBall when it comes to interpersonal relations.
* HypnotizeThePrincess: Gets hit with this in the Halloween special, courtesy of Vampire!Carl.
* IKnowKarate: She actually says this in "King of Mars."
* JerkassFacade: She's mostly a real jerk to Jimmy because she has a huge crush on him.
* JerkWithAHeartOfGold: Underneath her harsh, cynical surface she is a genuinely good person, if not at all fond of other people knowing about it:
** She is deeply infatuated with Jimmy and this is pretty much the main reason why she always tries to poke fun at him or otherwise make him angry. [[BelligerentSexualTension Works both ways]].
** She enjoys taking care of pets, plants and little babies.
* KungFuKid: Cindy practices karate. She goes to competitions, is sometimes seen in her gi, and although we're never told what level she's at, based on some of her flips, she's probably a black belt.
* TheLancer: Whenever she accompanies Jimmy on an adventure, much to his annoyance.
* LastNameBasis: She calls Jimmy by his last name (or the "Nerdtron" nickname she came up with) so often it comes as a shock to other kids when she actually uses his first name as well and even when she warms up to him towards the end of the show, it's not usual to hear a "Jimmy" coming out of her mouth, possibly because old habits die hard. To be honest, Jimmy himself does call Cindy "Vortex" every once in a while but not even nearly as often as she calls him Neutron (and when he does, it usually means he's ''extremely'' pissed off with her).
* LittleMissSnarker: Has her own moments:
** In "Trading Faces":
-->'''Jimmy in Cindy's body''': Don't give Cindy my astounding ability to create and build pioneering technologies, okay?
-->'''Cindy in Jimmy's body''': Oh yeah, like I'd want to invent toilet in a briefcase!
** "Beach Party Mummy" has this gem of an exchange:
-->'''Jimmy''': I don't understand it. I can't seem to find the lost tomb!
-->'''Cindy''': Duh! That's why they call it the "''lost'' tomb", not the "here it is tomb, come inside and have a milkshake"!
* LovingBully: She picks on Jimmy but she only does this to mask her love for him.
* NotSoDifferent: In regard to Jimmy. At least early in the series, she constantly makes fun of his alleged nerdiness whereas in fact she loves science just as much as he does, she just can't compare to him in terms of IQ. Also, while her [[AlphaBitch Alpha Bitchy]] demeanor would suggest otherwise, she isn't really even that much more popular with other kids than Jimmy: aside from Libby, she doesn't seem to have close friends or admirers (with basically only Jimmy, Timmy Turner and Eustace showing signs of having an actual crush on her).
* OnlySaneWoman: Every once in a while, especially seeing as Jimmy tends to lose the sight of the bigger picture and waste time using his inventions even when simpler means would suffice. However, since she's at least just as stubborn as Jimmy, her taing the helm doesn't always prove to be the best idea either.
* PinkMeansFeminine: Wears pink sneakers and, as seen in the first episode, [[PantyShot light-pink panties]]. Also wore a pink shirt in TheMovie. She also decorates her room pink.
* PuppyLove: With Jimmy.
* RichBitch: Played with. Her family does have a big mansion with a swimming pool (and even a butler) but Cindy herself is hardly a typical example of this trope: while it is shown in a couple episodes that she's rather greedy (to the point that she actually takes time to [[TheScrooge consider whether staying alive is worth of sacrificing her star rubys]]), she isn't really seen wearing fancy clothes and never once boasts about her family's alleged wealth. In "Granny Baby" she even holds a yard sale. So, we may assume that while her parents are definitely above the national average in terms of income, she doesn't benefit from it too much.
* TheRival: To Jimmy.
* SlapSlapKiss: With Jimmy. Are you starting to get an idea of their relationship yet?
* TomboyishPonytail: In the TV series.
* TookALevelInKindness: While by no means a bad person, Cindy tends to exhibit somewhat questionable morality, especially in the first two seasons of the show, when she was more often depicted as a semi-villain to Jimmy rather than just his likeable rival/love interest. She can still be a major pain in the butt come season 3 but nowhere near as much as before.
* {{Tsundere}}: Type A, obviously. In the original movie she explains that she only became one to Jimmy, because she was jealous of his better grades and hated his tendency to show off his intelligence on every given occasion.

[[folder:Liberty "Libby" Danielle Folfax]]
[[caption-width-right:248: "Hey Corky, you're going to need some hot funk for that show and I'm the girl who can bring it!"]]
->Voiced by: Crystal Scales

Cindy's best friend. The love of Libby's life? Music, the funkier the better. And she doesn't just listen, she also plays, DJ's, and has pipes that would make most opera singers sick.
* BetaBitch: She plays this role to her best friend Cindy.
* BetaCouple: With Sheen.
* BlackBestFriend: To Cindy.
%%* TheChick
* {{Fartillery}}: Gets this when she ate the Belch Boy packet in "The League of Villains" and proves to be ''better'' at it than Carl, given that she doesn't need seltzer or to be shaken to burp, and she can eventually control her burping to do it at will.
* {{Gasshole}}: Becomes one after eating the Belch Boy packet in "The League of Villains", even to the point of making a ''dance'' out of her burps.
* GiveGeeksAChance: Both in telling Cindy to be honest with Jimmy and her own involvement with Sheen.
* ImportantHaircut: Libby gets one in the ''Beach Party Mummy'' episode to fool a bunch of mummies that were chasing the gang. She keeps the new look for the remainder of the series.
* IncrediblyLongNote: Turns this into a ChekhovsGun in "The Great Egg Heist."
* {{Invisibility}}: She gained this power along with ability to [[BarrierWarrior generate force fields]] in "The N-Men" episode.
* OnlySaneWoman: Grows into this more and more as the series went on. By the end she's the most levelheaded character in the gang, much to her occasional frustration.
* PinkMeansFeminine: Her new design includes a pink long-sleeved shirt.
* PromotedToOpeningCredits: Libby is eventually in the title lineup at the end of the opening credits.
* PuppyLove: With Sheen.
* SassyBlackWoman: She's Cindy's sassy BlackBestFriend.
* SatelliteCharacter: Was originally one for Cindy, and several of her earliest appearances had her personality as more or less an echo of Cindy's, but as the characters got more development, she became more distinct, particularly regarding her love for music and fashion.
* ShipperOnDeck: She's FOREVER pleading with Cindy to just tell Jimmy how she feels and get it over with!
* TokenMinority: The only black girl in her group of friends.
* {{Tomboy}}: She adjusts really quickly to becoming "Burp Girl" in "The League of Villains", even proving better at using the sonic-blast burps than Carl did in "The N-Men".
* WomenAreWiser: Compared to her Love Interest, Sheen.
* YouthfulFreckles: Libby gained some in season 2 after her redesign.

->Voiced by: Creator/FrankWelker

Jimmy's robotic dog.
* AdvertisedExtra: Goddard is by all means a major character: he appears at least just as often as Jimmy's parents, Cindy and Libby and is featured prominently in the opening credits, but the first and only episode that gives him the focus is "Best in Show", one of the last ever aired. Other than that, his main occupation is to provide Jimmy with whatever piece of technology or information he is in need of at the moment.
* DoAnythingRobot: He does eleven billion and four things! Except clean up after himself.
* EatingMachine: There's several occasion where it lso eats human foods like ice cream.
* EyeBeams: Among other things it can do.
* JawDrop: It has its moment after seeing Jimmy dressed up for his date with Cindy. Being a mechanical robot, its jaw literally dropped.
* NonHumanSidekick: To Jimmy.
* RobotBuddy: Jimmy's mechanical canine.
* RobotDog: A robotic dog invented by Jimmy himself.
* SelfDestructMechanism: Its "plays dead" command is this. Goddard can reassemble itself despite its core combustion. This ability is vital to defeat Eustace's [[PowerCopying Robo Adaptoy]].
* TheSpeechless: Except in the movie, where his options for Jimmy are read in a robotic voice.
%%* TeamPet

[[folder:Hubert "Hugh" Beaumont Neutron]]
[[caption-width-right:195:"Hi, Puffmomma. Remember how I promised I'd never be brought home by an angry mob again?"]]
->Voiced by: Mark [=DeCarlo=]

Jimmy's father. Averts Father Knows Best. Nevertheless, he's a chipper, upbeat family man who always has time to dispense words of wisdom for Jimmy, even if most of the time those words are better left ignored. Has an obsession with ducks.
* AdultsAreUseless: Played straight with Jimmy's dad in the TV series, who is probably one of the biggest idiots in the city.
* BumblingDad: Many times, Hugh would screw up one of Jimmy's inventions.
* {{Cloudcuckoolander}}: Quite possibly the largest one in the series.
* TheDitz: The typical dim-witted bumbling father.
* {{Gasshole}}: Even without drinking the Burping Soda, Hugh has burped more than anyone else in the series, including Carl.
* HappilyMarried: To Judy.
* IdiotBall: Holds it consistently, like it's his firstborn child.
* JumpOffABridgeRebuttal: Twisted.
--> '''Jimmy''': "Aw, but Dad! All my friends are going!"
--> '''Hugh:''' "Now, Son, [[IceCreamKoan if all your friends were named Cliff, would you jump off them?]]"
* ObliquelyObfuscatedOccupation: Eventually averted when we learn he's a car salesman.
* TookALevelInJerkass: Twice as a result of Jimmy's inventions.
** The first is when Jimmy altered the past so that his dad would invest his only money ($50) into then non-popular restaraunt [=McSpankies=], to make his parents rich and allowing him to get an expensive set of encylopedias that he wants. Unfortunately along with Judy, he becomes a snobby rich man with no interest in his son, forgetting his name, and offering him some money to leave. He even refuses help pay for a lifesaving operation for his father merely because he does not want to lose any money.
** The second is when Jimmy uses a machine to turn him cool (and prevent him from embarassing him at the Fathers Day performances at school). He becomes super popular with the town, but never wants to spend time with Jimmy or Judy anymore and plans to leave them to go on a World Tour as a popstar. He even initially ''refuses to save his son's life'' before his parental instincts finally kick in and revert him back to normal.
* TrademarkFavoriteFood: Pie.
* UglyGuyHotWife: With Judy.

[[folder:Judith "Judy" Neutron]]
[[caption-width-right:300:"To think, I stepped out for two measly days and you replace me with some psycho robot with a hideous 1950's hairdo?"]]
->Voiced by: Megan Cavanagh

Jimmy's mother. She's happy to cook and clean and run the household but does want some appreciation for all she does. After all without her, Jimmy and Hugh's lives fall to pieces.
* ActionMom: She's incredibly athletic, coordinated, intelligent, and she keeps a plasma rifle in her utility closet (for those tough ground-in stains!)
%%* BeautyMark
* DitzyGenius: Not ditz per se (she's certainly the intelligent one in her marriage with Hugh and more rational than he is) but she has her moments of ditziness. There are also numerous moments where she demonstrates it's definitely from her side of the gene pool that Jimmy gained his intellect.
* FullNameUltimatum: "James Issac Neutron!"
* {{Gasshole}}: Becomes this after chugging some of Jimmy's Burping Soda.
* HappilyMarried: To Hugh.
* HypnotizeThePrincess: Ever noticed she gets hypnotized quite a bit on this show?
* MamaBear: "'''Get away from my family, you ugly bucket of bolts!'''"
* MundaneUtility: Use a demolecular cannon beam to clean difficult stains.
%%* OnlySaneWoman
* StacysMom: Carl has a crush on her.
* UglyGuyHotWife: With Hugh.
* WomenAreWiser: Compared to her bumbling husband.

[[folder:Nick Dean]]
[[caption-width-right:215:"You know, these are as cool as... me!"]]
->Voiced by: CandiMilo

The "cool guy" that everybody loves at school, especially the girls.
* BadButt: Before his later characterization took hold.
* ButtMonkey: All of his later appearances consist of him breaking his leg while skateboarding. Jimmy lampshades this during one of his news segments in "Lady Sings the News."
* TheCharmer: Thanks to his AllGirlsWantBadBoys charm.
* ChickMagnet: All the girls find him attractive.
* DemotedToExtra: Earlier episodes were building him up to be an important character. Then he vanished. Now he barely shows up at all except to break his leg skateboarding. He even got his own toy in the Wendy's Kid's Meals when the original film came out.
* {{Flanderization}}: In the movie, Jimmy takes backseat as Nick leads the charge against the Yolkians, and the class BadButt even manages to take out a couple of Yolkian guards by hijacking one of their spears... only to lose momentum upon seeing the giant alien-chicken, at which point he becomes completely useless and Jimmy has to lead the charge himself. Nick's later Paper Tiger characterization suggests he would balk at even taking on the guards, if he had to do it again.
* GratuitousGerman: He sang a lullaby in German to his twonkie, and knowing how twonkies respond to song, it's expected what happened to him.
* KidAnova
* PaperTiger: He's the ultimate cool dude, the girls all dig him, and he's supposed to be tough. In the movie, his part of the plan is to take care of the BigBad while the others rescue their parents. One look at his competition, though, and he goes screaming like a little girl. And it only goes downhill from there…
* PrettyBoy
* ScreamsLikeALittleGirl: Whenever something frightens him.
* TroubledButCute: A supposed tough kid who is considered cool and is popular with girls.

[[folder:Bolbi Stroganovsky]]
[[caption-width-right:210:Vote for Bolbi!]]
->Voiced by: Creator/PhilLaMarr
* BunnyEarsLawyer: As silly and strange as he is, he's an excellent actor.
* ButtMonkey: In "El Magnifico" he pays a slapstick-heavy price so that Mr. Estevez can pull of his superhero hoax in front of Sheen. Not that anyone asked him to.
* {{Cloudcuckoolander}}: He makes ''Sheen'' look sane by comparison.
* DanceSensation: The "Slap Dance" from his homeland. [[EarWorm "Slap slap slap! Clap clap clap! Slap slap slap! Clap clap clap!"]]
* TheDitz: Though he seems like just a goofy foreigner at first.
* FunnyForeigner: Kind of like [[Series/That70sShow Fez]] or [[WesternAnimation/EdEddNEddy Rolf]]. The difference is that Bolbi's country is actually named ([[PunnyName Backhairistan]]).
* HiddenDepths: He's a very good actor and has monologues committed to memory.
* StrongFamilyResemblance: His sister is just a slightly shorter version of him in blonde braids.
* TheSixthRanger: Starts taking a role similar to this in later episodes.
* TrademarkFavoriteFood: Kebabs. They appear to be standard cuisine in his country.
* VocalEvolution: Had a slightly deeper voice and heavier accent in his first appearance.

[[folder:Betty Quinlan]]
[[caption-width-right:248:"Betty is a woman."]]
->Voiced by: Creator/KathSoucie

The girl of Jimmy's dreams, and sometimes the motivation for hi jinks in his effort to impress. Cindy doesn't care for her... for ''some'' reason.
* BareYourMidriff: When she played Lady Macbeth.
* BettyAndVeronica: Quite literally the sweet natured Betty to Cindy's Veronica.
%%* BeautyMark
* TheRival: Unintentionally to Cindy.
* ShallowLoveInterest: For the most part. She doesn't get any true focus outside of Jimmy's love glazed POV. Finally subverted a bit when we see, that despite her pleasant demeanor, she ''does'' have her limits. And no, she's ''not'' oblivious to Jimmy's crush on her (she'd have to be deaf, dumb, and blind, actually), or Cindy's crush on Jimmy for that matter. [[spoiler: She lets Cindy have him.]]

[[folder:The Twonkies]]

* BerserkButton: '''''MUSIC'''''. Seems to have stopped after their first appearance, though, as one can be seen during a big musical number at one point.
* TheCameo: They can be seen appearing in a brief time in several episodes, can even be seen several times in one episode.
* FishEyes: They have them.
* KillerRabbit
** VillainDecay: After their first appearance, Twonkies are treated as if they were normal rabbits.
* MonsterOfTheWeek: In ''Attack of the Twonkies''. They later became {{Recurring Extra}}s.

[[folder:Winnifred Fowl]]
->Voiced by: Andrea Martin

The cast's homeroom teacher.
* AnimalMotifs: Birds. Not just her name, but her appearance (long pointy nose, motioning her arms like wings, squawking, etc.).
* BunnyEarsLawyer: As odd as she is, she has proven many times to be a ReasonableAuthorityFigure.
* {{Cloudcuckoolander}}: Occasionally teaches subjects that really aren't pertinent to a fourth grade education ("And that's why cowboys are bow-legged" anyone?).
* DeathGlare: Unlike the other staff members at the school, she doesn't require a weapon to take down the unruly substitute teacher parents in "How To Sink A Sub". She uses her "skunk eye", which immediately intimidates people into backing down.
* GagNose: Resembling a beak, taking her whole bird motif much further.
* KavorkaMan: A rare female example. She attracted Thomas Edison, went dancing with President Hoover, flirts with Sam and was once married to a werewolf.
* NoodleIncident: She was once married to a werewolf. She refers to it as "a story for another day".
* SternTeacher: She has her moments.
* VagueAge: Okay, she's old. But ''how'' old is she? In one episode, she implies that 58 is ''young'' for her.
* VerbalTic: Tends to end sentences with a squawk-like noise.

Owner of the local hangout joint, The Candy Bar.
* BullyingADragon: Does so in the superhero episode the N-Men. Jimmy is a [[IncredibleHulk rampaging orange monster]] but upon seeing his parents, he starts calming down. Until Sam [[TooDumbToLive decides to throw fruit]] in Hulk/Jimmy's face. Needless to say, the mutated Jimmy doesn't take too kindly to it. This also came up in the HalloweenEpisode, though he had an angry mob to back him up.
%%* DeadpanSnarker
* {{Jerkass}}: N-Men episode again. [[JerkassHasAPoint Granted something should have been done to try to help the kids control their new found powers.]] However, calling the military up to ''imprison'' them and then telling the kid's parents they were just ''freaks''?
* ShipTease: Sometimes has these with Ms. Fowl.
* VerbalTic: Has a habit of ending his sentences with, "Yeah!".

[[folder:King Goobot]]
->Voiced by: Creator/PatrickStewart (movie), S. Scott Bullock (TV series)

King of the Yolkians, and Jimmy Neutron's archenemy.
* ArchEnemy: To Jimmy.
* BigBad: Of the movie.
* LegionOfDoom: He created "League of Villains" consisting of several villains from numerous episodes including some of the Rogue Galleries.
* TaughtByExperience: Goobot learned from past experiences that Goddard, Jimmy's inventions and friends were things that foiled his plans so he cut down Jimmy's access to them before catching him in "League of Villains".
* TrappedInThePast: What presumably becomes his ultimate fate at the end of League of Villains episode. Considering that we see Eustace Strych in third crossover with WesternAnimation/TheFairlyOddParents, he's presumably able to go out.

[[folder:Professor Finbarr Calamitous]]
->Voiced by: Creator/TimCurry

Jimmy's arch-nemesis and the show's most recurring antagonist.
* AbsentMindedProfessor: Calamitous when introduced was never able to finish anything, even his own sentences. From his second appearance onwards, he can now talk in complete sentences thanks to self-help classes. However, this habit appears again in "League of Villains".
* ArchEnemy: Seems to have taken this role up from King Goobot, as he's one of Jimmy's most recurring enemies.
* BewareTheSillyOnes: Even before he took self-help classes to help him finish things, he was still as threatening as he was forgetful in his first appearance. Jimmy himself lampshades this:
-->'''Jimmy:''' "For a bumbling genius, he's pretty dangerous."
* BigBad: Expect him to fall into this role a lot, especially during crossovers.
* DopeSlap: Often gets these from his daughter.
* EvilCounterpart: To Jimmy, although he's much older.
* InTheirOwnImage: After being fused with [[WesternAnimation/TheFairlyOddParents von Strangle]], he intended to recreate all reality as he saw fit.
* LoopholeAbuse: His mini-mecha is basically the only functional piece of equipment he has because he technically never put in a bathroom; everything else he has is usually missing a key component of some sort. It's implied that the whole bathroom bit is how he mentally got over not "completing" it.
* MadScientist: He even has the look, the EvilLaugh, and a [[MadScientistsBeautifulDaughter beautiful daughter.]]
* MiniMecha: A humanoid red model was his best work in his debut. The only thing he hadn't finished was putting in a bathroom.
* TakeOverTheCity: In his first appearance. Jimmy assumes he's just gonna take over the world, but he says he's going for something smaller.
* WouldHurtAChild: Considering the showdown he usually has with Jimmy, this trope suits him. In crossover with WesternAnimation/TheFairlyOddParents, he ouright tried to kill him using Jorgen's magic. Thankfully, fairy magic is not made to harm.

[[folder:Beautiful Gorgeous]]
->Voiced by: Wendie Malick

Professor Calamitous's daughter. Her real name's Georgia Calamitous. Jimmy, Carl, and Sheen are easily seduced by her looks.
* AnnoyingLaugh: Snorting variation in every full, uninterrupted EvilLaugh. Sheen even lampshades it.
* BeautyMark: On her right cheek near the upper lip.
* BeleagueredAssistant: In ''Operation: Jet Fusion''. She often bemoans having to do Calamitous's dirty work and put up with his eccentricities.
* BondVillainStupidity: She devised a death trap for Jimmy and Jet Fusion instead of killing them directly like majority of Bond villain. Considering her debut is in an episode parodying spies film, it's to be expected.
* DeadpanSnarker: She often has something snarky to say.
* DudeMagnet: How every guy in the show reacts towards her.
* IKnowKarate: To be accurate, she knows 112 forms of martial arts. She proved her prowess by getting the upper hand on Jet Fusion.
* ImpossibleHourglassFigure
* InterspeciesRomance: With Junkman due to Jimmy's LovePotion.
* MadScientistsBeautifulDaughter: Her name is half James Bond Reference, half beating this trope over your head.
* MeaningfulName: Her dad wasn't exactly very creative with the name. Or subtle.
* MindControlDevice: She made one to hypnotize Jet Fusion in the form of a box candy. Also did this Jimmy with his HypnoRay.
* MsFanservice: The name should be a tip off, but the way Jimmy, Sheen and Carl react to her in her debut pretty much cements it.
* RunningGag: Every time she mentions she wanted to have a certain career other then villainy, she always gets interrupted or cut off. [[spoiler: It was to make [[WhatTheHeckIsAnAglet aglets]] for a living.]]
* ThenLetMeBeEvil: Apparently she never wanted to be evil; just felt obligated to because her father was doing it. [[InTheBlood Then comes "My Big Fat Spy Wedding"...]]
* UglyGuyHotWife: With Junkman.

->Voiced by: Creator/TimAllen

The host of the hit game show "Intergalactic Showdown" and [[BigBad the main villain]] of the TV movie "Win Lose and Kaboom".
* BigBad: Of "Win Lose And Kaboom".
* DoingInTheWizard: His seemingly supernatural hold over reality, time and space is actually caused by a pair of matrix generators hidden in his cuff links.
* FauxAffablyEvil: Rarely drops his cheery, hammy attitude even while threatening to ''blow up people's planets''. At the end, he finally stops and decides to [[LetsGetDangerous get serious]].
* {{Hypocrite}}: Insists during the race that there's no cheating allowed, but permits the Brains to put Jimmy and the gang into a LotusEaterMachine. Later he panics at the idea of his quadrant being blown up despite the fact that his entire show is about blowing up completely innocent planets simply because their species [[DisproportionateRetribution lost a game]].
* KarmaHoudini: The worst he gets is being forced to hand over his show to the Brain aliens and advertise an exercise machine that implements ElectricTorture. Probably justified as he's implied to be indestructible.
* LargeHam: He's a GameShow host. It comes with the territory.
* OmnicidalManiac: "Winner gets a brand new car! Loser gets their home planet ''destroyed!''"
* TheOmnipotent[=/=]RealityWarper: Thanks to the matrix generators in his cuff links.
* SmugSnake: He's definitely dangerous, but his pride makes him rather short-sighted.
* TimeAbyss: Implied, as April states that his show has existed for eons.
* VillainousBreakdown: Loses it when he discovers that his show is about to be destroyed.

[[folder:Zix, Travoltron, and Tee]]
->Voiced by: Creator/MauriceLaMarche (Zix), Creator/JeffBennett (Travoltron), Creator/KevinMichaelRichardson (Tee)

A group of Trio Space Bandit Jimmy and friends met when they tried to dig Asteruby. Later they tried to sell shrunk Retroville townspeople as toys and joined "League of Villains" created by Goobot.
* ArmorPiercingQuestion: After having a HeelFaceTurn of his own, Tee uses one of these on Zix and Travoltron to make them undergo one.
-->'''Tee:''' Well why ya gotta be villains?!\\
''(Both Zix and Travoltron stammer trying to find an answer and failing)''
* ButtMonkey: Tee was treated as this by his fellows in League of Villains. This and Sheen's willing to hear his story were what triggered his HeelFaceTurn.
* {{Expy}}:
** Tee is an alien who talks and acts like Creator/MrT.
** Travoltron acts like Creator/JohnTravolta. Or at least his character in Film/SaturdayNightFever. His name is presumably even a parody of John Travolta's last name.
** The third one, Zix, talks like Jon Lovitz. A bit more devious than Jon Lovitz though...
* GoodFeelsGood: What Zix and Travoltron thought after helping Jimmy and friends, indicating that their HeelFaceTurn would be permanent.
* FingerGun: All three of them use this motion when shooting some kind of gooey substance used in sealing Jimmy's lab.
* HeelFaceTurn: Tee during Jimmy and Sheen's imprisonment. Zix and Travoltron followed during the casts' time in Cretaceous Era.
* ManHug: Tee really likes to give this. [[CuddleBug Well, a bit too much]]. Travoltron too, to a lesser extent.
* RealMenHateAffection: In contrary to Tee and Travoltron, Zix hates ManHug but he will accept a handshake with his teammates.
* SpeaksFluentAnimal: They can only understand and speaks lizards language though since they said they were in the same family as them. They used this ability to distract and send a T-rex away from eating Jimmy and his friends.
* VerbalTic: Tee tends to have "Fool!" in most of his sentence.


[[folder:Edward "Eddie" Neutron]]
->Voiced by: Mark [=DeCarlo=]

Jimmy's 17,5-month-old cousin commonly called by people as "baby Eddie". Despite his baby-looking appearance, he's actually very genius; capable of walking, speaking fluently, and devising plan to kill all of Neutron family member. He's one of members of "League of Villains" created by Goobot.
* BrainyBaby: A baby capable of reading, walking, talking and various things human adults can do, except changing his own diapers and controlling his excretion/digestive system.
* BitchInSheepsClothing: His first appearance. Since his identity had been covered, he dropped the nice appearance in subsequent appearances.
* CasanovaWannabe: Tried flirting with Beautiful Gorgeus with negative results.
* CharlieBrownBaldness: Has one visible gravity-defying strand of hair only. Justified somehow that he's still a baby.
* CoolBike: His motorcycle can frickin' ''bring him to space''. Too bad it only appeared in "Bad guys assemble montage" at the beginning of "League of Villains" episode.
* EnfantTerrible: Duh.
* EvilGenius: Who knows a 17,5-month-old baby can outsmart Jimmy ar first, and almost succeed in killing his family members using Jimmy's own things?
* EvilSoundsDeep: He has a really deep voice, a clear contrast to [[VocalDissonance his petite appearance]].
* {{Expy}}: He has several similarities with [[WesternAnimation/FamilyGuy Stewie Griffin]], both are [[BrainyBaby baby geniuses]] with a rather unbabylike attitude.
* OnlySaneMan: Putting aside his need to change diapers, he's mostly this with King Goobot.
* RunningGag: He kept asking his fellow teammates to change his diaper with no success. The joke came in full circle when he took off his own 5-day-old diaper to chase a T-rex away.
* StatingTheSimpleSolution: While other members of League of Villain debated on how to kill Jimmy Neutron using convoluted (or even silly) ways, he stepped up and said "Just blow him into deep space!" to which everyone agreed.

[[folder:Eustace Strych]]
-> Voiced by: Creator/RobPaulsen

A snobby rich kid who buys all of his gadgets from his dad. He's one of members of "League of Villains" created by Goobot.
* BadBoss: He uses his personal butler, Blix as an abuse dummy.
* EvilBrit: Has a UsefulNotes/{{British Accent|s}} to go with his rich jerk persona.
* EvilCounterpart: To Jimmy. They both have a lot of high-tech gadgets, but while Jimmy is usually well-behaved and makes them himself, Eustace has his inventions bought while he's a spoiled brat.
* {{Jerkass}}: He's very rude to everyone, especially Jimmy. And he was using Cindy's love to emotionally crush Jimmy.
* PragmaticVillainy: Forms an EnemyMine with Jimmy and his pals in "King of Mars" when [[SiliconBasedLife the Martians]] try to destroy it. Not because of any moral reasons, mind you, but because Earth is "where he keeps all his stuff".
* RichBastard: While his billionaire dad is a decent guy, Eustace himself is a selfish jerk.
* SanitySlippage: Later episodes imply that his vendetta against Jimmy has left him with a few screws loose. He even lampshades this trope ''while [[LaughingMad laughing insanely]]!''
* SmugSnake: Probably one of the less threatening antagonists Jimmy has faced.
* SoreLoser: Whenever he loses a competition, he has Blix bend down while he kicks him in the rear repeatedly.
* SpoiledBrat: His father has difficulty disciplining him until Hugh encourages him to do so. When his dad finally punishes him for his misbehavior, he just yells at him while crying when he's sent to his room.
* TantrumThrowing: Done when he's kicking his butler.