Characters / The Adventures of Jimmy Neutron: Boy Genius

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    James "Jimmy" Isaac Neutron
"Gotta blast!"
Voiced by: Debi Derryberry

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?
  • Aesop Amnesia: At least half of the episode plots wouldn't happen if Jimmy would remember how often his inventions backfired.
  • Anime Hair: Lampshaded consistently.
  • Belligerent Sexual Tension: With Cindy.
  • Berserk Button: Do NOT give Jimmy an F. Denzel Crocker in the Jimmy Timmy Power Hour learns this the hard way.
  • Big Damn Heroes: ALL THE TIME. Often Lampshaded, in fact.
  • Big "NO!": In The Tomorrow Boys, after learning he gets married to Cindy. In a bit of Leaning on the Fourth Wall, 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* "NOOOOOOOOOOOOOOOOOO!" *shot of him from up, and then zooms out to Retroville and Earth*
  • Black Sheep: 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 caused the problem in the first place.
  • Brilliant, but Lazy: 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.
  • Bungling Inventor: While he's undoubtedly a genius, the plots of most episodes are kicked off when his inventions go haywire.
  • Butt Monkey: His inventions usually cause troubles. And when it doesn't come to his inventions, he's picked on by those left and right.
  • Cassandra Truth: 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.
  • Catch Phrase: 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.)
  • Child Prodigy: A preteen genius who has an IQ of 210.
  • Crazy-Prepared: 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.
  • Deadpan Snarker:
    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 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.
  • Fatal Flaw: 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.
  • Future Loser: In the 'Bad Future' of The Tomorrow Boys, Future!Jimmy is a slack-jawed loser, wanted by the evil dictator Libby, with a five-o'clock shadow and Cindy as a wife. Current!Jimmy is less than impressed.
  • Gadgeteer Genius: 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 "Flowers for Algernon" Syndrome.
  • Get Back to the Future: Jimmy's dad screwed up with one of his inventions, leaving him, Carl and Sheen in the past.
  • He Cleans Up Nicely:
    • 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, 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.
  • Height Angst: 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.
  • "Hell, Yes!" Moment: 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.
  • Idiot Hero: 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.
  • I'm Your Worst Nightmare: 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?"
  • Insufferable Genius: At times, but often more pronounced when Cindy's around.
  • Intelligence Equals Isolation: 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.
  • Kid Hero: Jimmy is only 10.
  • Little Professor Dialogue: Justified partially in that he does actually have an IQ of 210.
  • Nerds Are Innocent: He's a child prodigy who loves and excels at science...and still believes in cooties.
  • Nice Job Breaking It, Hero: 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 Black Sheep as a result. However, this trope is used less and less in later episodes.
  • Pet's Homage Name: 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.
  • Properly Paranoid: He knew better than to trust the Yolkians in "The Eggpire Strikes Back."
  • Puppy Love: With Cindy.
  • Ridiculously Successful Future Self: In the 'good future' of The Tomorrow Boys, Jimmy is the first person to ever win the Nobel Prize in bulk.
  • Rival Turned Evil: In The N-Men...
  • Science Hero: He embodies this trope for kids shows, along with Dexter.
  • Sesquipedalian Loquaciousness: A frequent user and abuser.
  • Slap-Slap-Kiss: With Cindy. All the time.
  • The Smart Guy: Duh.
  • Took a Level in Dumbass: When he accidentally drained his brain too much in Normal Boy.
  • TV Genius: He is an elementary school student who is not only excessively prone to Techno Babble and Sesquipedalian Loquaciousness, 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.
  • Yank the Dog's Chain: One of Jimmy's signature flaws. When some of his inventions start off good, then backfire on him right afterwards.

    Carlton "Carl" Ulysses Wheezer
"You look like a couple of intelligent young men!"
"Nuh uh, it's just the glasses."
Voiced by: Rob Paulsen

Jimmy's shy, asthmatic best friend who has an unhealthy obsession with llamas and Jimmy's mom.
  • Big Eater: 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 Extreme Omnivore for laughs:
    Carl: I don't eat newspapers! (Beat) Well, I'm trying to quit.
  • Catch Phrase: "My scapula..."
  • Fartillery: Gets this in "The N-Men" (see Gasshole below).
  • Fat Best Friend: 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 sonic blast burps by drinking seltzer or shaking himself really hard.
  • Green-Eyed Monster: Implied quite heavily in "I Dream of Jimmy" and "Carl Wheezer, Boy Genius" that he'd really like to have Jimmy's life.
  • Hollywood Tone-Deaf: His most attempts at singing something.
  • It Runs in the Family: His allergies. Turns out his mother and father have various allergies too.
  • Jerkass Ball: 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.
  • Likes Older Women: 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.
  • Loose Lips: Sheen helps him a lot with this one. They're often the ones to reveal the secret plan to the enemy, generally via Suspiciously Specific Denial.
  • Minor Injury Overreaction: 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.
  • Nerd Glasses: Wears a pair of big glasses.
  • Nerds Are Innocent: 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.
  • Nerdy Inhaler: Carl uses an inhaler very frequently and is also allergic to almost everything.
  • Precocious Crush: On Jimmy's mom.
  • Shrinking Violet: He's generally shy and nervous.
  • Sickly Neurotic Geek: What else can you expect with a surname like 'Wheezer'?
  • Stalker with a Crush: To Jimmy's mom.
  • Voice Changeling: 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.
  • Youthful Freckles: Has many freckles that match his red hair.

    Sheen Juarrera Estevez
"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.
  • Accent Adaptation: 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".
  • Badass Boast: In Sheen's Brain.
    I control the wind, and I shall rain fire down from the heavens! Goodbye Sheen the overlord. Hello Sheen the God!
  • Berserk Button: Do NOT call Ultra-Lord a doll. Or mock Ultra-Lord in any way.
  • Beta Couple: With his sweet princess, Libby.
  • Breakout Character: Gets his own Spin-Off, Planet Sheen.
  • 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.
  • The Ditz: His IQ is 32.
  • Drunk with Power: When his intelligence is increased in Sheen's Brain.
  • Early Installment Weirdness: He mentions a sister in "I Dream of Jimmy" but Word of God has said since to disregard it. Canonically, Sheen is an only child who lives with his father and grandmother (at least until Planet Sheen).
  • Extraverted Nerd: An eccentric comic book-loving nerd.
  • Genius Ditz: He has enough smarts to write a website, at least. Granted, said website is filled with inaccuracies about 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.
  • Goofy Print Underwear: Limited Edition Ultra Lord Underwear! Only available in Japan!
  • Hollywood Tone-Deaf: His singing is so bad, it actually puts the music-hating Twonkies to sleep.
  • Keet: He's very energetic.
  • Loony Fan: He's obsessed with cartoon superhero Ultra Lord.
  • Loose Lips: See above.
  • Meta Guy: A lot of his Non Sequiturs are lampshades, especially as the show went on. A Running Gag 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 "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..."
  • Missing Mom: According to the creators, she died when Sheen was little.
  • Plucky Comic Relief: He serves as the funny sidekick on the show.
  • Puppy Love: With Libby.
  • The Slacker: Watches Ultra-Lord while trying to do his homework
  • The Watson: Has his moments.

    Cynthia "Cindy" Aurora Vortex
"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.
  • Academic Alpha Bitch: 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.
  • Academic Athlete: The smartest student after Jimmy and knows karate enough to kick asses.
  • Action Girl: Cindy practices karate.
  • Bare Your Midriff: As Special Girl.
  • Belligerent Sexual Tension: With Jimmy.
  • Cannot Spit It Out: More because of pure stubbornness than anything, really.
  • Clingy Jealous Girl: She doesn't like seeing Jimmy showing interest in other girls.
  • Deadpan Snarker: Often prone to snide remarks.
  • Defrosting Ice Queen: Towards Jimmy over the course of the show. Her love for him becomes more evident.
  • Expy: Of Helga Pataki. Both harbor crushes on the main protagonist but act villainous and bullying whenever they're present, to hide it.
  • Genius Bruiser: Other than being smart, Cindy is more athletic than Jimmy and practices a lot of martial arts sports.
  • Girlish Pigtails: In the movie.
  • Goofy Print Underwear: Polka dot panties.
  • Green-Eyed Monster: 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.
  • Hint Dropping: Unfortunately, Jimmy seems to permanently be holding the Idiot Ball when it comes to interpersonal relations.
  • Hypnotize the Princess: Gets hit with this in the Halloween special, courtesy of Vampire!Carl.
  • I Know Karate: She actually says this in "King of Mars."
  • Jerkass Façade: She's mostly a real jerk to Jimmy because she has a huge crush on him.
  • Jerk with a Heart of Gold: Despite being mean to Jimmy, she really does care about him deep down.
  • Kung-Fu Kid: 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.
  • Little Miss Snarker: Has her own moments:
    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!
  • Loving Bully: She picks on Jimmy but she only does this to mask her love for him.
  • Pink Means Feminine: Wears pink sneakers and, as seen in the first episode, light-pink panties. Also wore a pink shirt in The Movie. She also decorates her room pink.
  • Puppy Love: With Jimmy.
  • The Rival: To Jimmy.
  • Slap-Slap-Kiss: With Jimmy. Are you starting to get an idea of their relationship yet?
  • Tomboyish Ponytail: In the TV series.
  • 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.

    Liberty "Libby" Danielle Folfax
"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.
  • 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.
  • Important Haircut: 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.
  • Incredibly Long Note: Turns this into a Chekhov's Gun in "The Great Egg Heist."
  • Only Sane Woman: 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.
  • Pink Means Feminine: Her new design includes a pink long-sleeved shirt.
  • Promoted To Opening Credits: Libby is eventually in the title lineup at the end of the opening credits.
  • Puppy Love: With Sheen.
  • Sassy Black Woman: She's Cindy's sassy Black Best Friend.
  • Satellite Character: 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.
  • Shipper on Deck: She's FOREVER pleading with Cindy to just tell Jimmy how she feels and get it over with!
  • Token Minority: 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".
  • Women Are Wiser: Compared to her Love Interest, Sheen.
  • Youthful Freckles: Libby gained some in season 2 after her redesign.

Voiced by: Frank Welker

Jimmy's robotic dog.
  • Do-Anything Robot: He does eleven billion and four things! Except clean up after himself.
  • Eating Machine: There's several occasion where it lso eats human foods like ice cream.
  • Eye Beams: Among other things it can do.
  • Jaw Drop: It has its moment after seeing Jimmy dressed up for his date with Cindy. Being a mechanical robot, its jaw literally dropped.
  • Non-Human Sidekick: To Jimmy.
  • Robot Buddy: Jimmy's mechanical canine.
  • Robot Dog: A robotic dog invented by Jimmy himself.
  • Self-Destruct Mechanism: Its "plays dead" command is this. It can reassemble himself after exploding.
  • The Speechless: Except in the movie, where his options for Jimmy are read in a robotic voice.

    Hubert "Hugh" Beaumont Neutron
"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.

    Judith "Judy" Neutron
"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.
  • Action Mom: She's incredibly athletic, coordinated, intelligent, and she keeps a plasma rifle in her utility closet (for those tough ground-in stains!)
  • Ditzy Genius: 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.
  • Full Name Ultimatum: "James Issac Neutron!"
  • Gasshole: Becomes this after chugging some of Jimmy's Burping Soda.
  • Happily Married: To Hugh.
  • Hypnotize the Princess: Ever noticed she gets hypnotized quite a bit on this show?
  • Mama Bear: "Get away from my family, you ugly bucket of bolts!"
  • Mundane Utility: Use a demolecular cannon beam to clean difficult stains.

    Nick Dean
"You know, these are as cool as... me!"
Voiced by: Candi Milo

The "cool guy" that everybody loves at school, especially the girls.
  • Bad Butt: Before his later characterization took hold.
  • Butt Monkey: 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."
  • The Charmer: Thanks to his All Girls Want Bad Boys charm.
  • Chick Magnet: All the girls find him attractive.
  • Demoted to Extra: 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 Bad Butt 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.
  • Gratuitous German: He sang a lullaby in German to his twonkie, and knowing how twonkies respond to song, it's expected what happened to him.
  • Kid-anova
  • Paper Tiger: 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 Big Bad 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…
  • Pretty Boy
  • Screams Like a Little Girl: Whenever something frightens him.
  • Troubled, but Cute: A supposed tough kid who is considered cool and is popular with girls.

    Bolbi Stroganovsky
Vote for Bolbi!
Voiced by: Phil LaMarr

    Betty Quinlan
"Betty is a woman."
Voiced by: Kath Soucie

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.
  • Shallow Love Interest: 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. She lets Cindy have him.

    The Twonkies 

  • Berserk Button: MUSIC. Seems to have stopped after their first appearance, though, as one can be seen during a big musical number at one point.
  • Continuity Cameo: They can be seen appearing in a brief time in several episodes, can even be seen several times in one episode.

    Winnifred Fowl 
The cast's homeroom teacher.
  • Animal Motifs: Birds. Not just her name, but her appearance (long pointy nose, motioning her arms like wings, squawking, etc.).
  • Cloudcuckoolander: Occasionally teaches subjects that really aren't pertinent to a fourth grade education ("And that's why cowboys are bow-legged" anyone?).
  • Death Glare: 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.
  • Gag Nose: Resembling a beak, taking her whole bird motif much further.
  • Kavorka Man: A rare female example. She attracted Thomas Edison, went dancing with President Hoover, flirts with Sam and was once married to a werewolf.
  • Noodle Incident: She was once married to a werewolf. She refers to it as "a story for another day".
  • Stern Teacher: She has her moments.
  • Vague Age: Okay, she's old. But how old is she? In one episode, she implies that 58 is young for her.
  • Verbal Tic: Tends to end sentences with a squawk-like noise.

Owner of the local hangout joint, The Candy Bar.

    King Goobot 
Voiced by: Patrick Stewart (movie), S. Scott Bullock (TV series)

King of the Yolkians, and Jimmy Neutron's archenemy.
  • Arch-Enemy: To Jimmy.
  • Big Bad: Of the movie.
  • Legion of Doom: He created "League of Villains" consisting of several villains from numerous episodes including some of the Rogue Galleries.
  • Trapped in the Past: What presumably becomes his ultimate fate at the end of League of Villains episode. Considering that we see Eustace Strych in third crossover with The Fairly OddParents, he's presumably able to go out.

    Professor Finbarr Calamitous 
Voiced by: Tim Curry

Jimmy's arch-nemesis and the show's most recurring antagonist.
  • Absent-Minded Professor: 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".
  • Beware the Silly Ones: 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."
  • Big Bad: Expect him to fall into this role a lot, especially during crossovers.
  • Evil Counterpart: To Jimmy, although he's much older.
  • In Their Own Image: After being fused with von Strangle, he intended to recreate all reality as he saw fit.
  • Loophole Abuse: 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.
  • Mad Scientist: He even has the look, the Evil Laugh, and a beautiful daughter.
  • Mini-Mecha: A humanoid red model was his best work in his debut. The only thing he hadn't finished was putting in a bathroom.
  • Take Over the City: In his first appearance. Jimmy assumes he's just gonna take over the world, but he says he's going for something smaller.
  • Would Hurt a Child: Considering the showdown he usually has with Jimmy, this trope suits him. In crossover with The Fairly OddParents, he ouright tried to kill him using Jorgen's magic. Thankfully, fairy magic is not made to harm.

    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.
  • Bond Villain Stupidity: 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.

Voiced by: Tim Allen

The host of the hit game show "Intergalactic Showdown" and the main villain of the TV movie "Win Lose and Kaboom".
  • Big Bad: Of "Win Lose And Kaboom".
  • Doing In the Wizard: His seemingly supernatural hold over reality, time and space is actually caused by a pair of matrix generators hidden in his cuff links.
  • Faux Affably Evil: Rarely drops his cheery, hammy attitude even while threatening to blow up people's planets. At the end, he finally stops and decides to 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 Lotus-Eater Machine. 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 lost a game.
  • Karma Houdini: The worst he gets is being forced to hand over his show to the Brain aliens and advertise an exercise machine that implements Electric Torture. Probably justified as he's implied to be indestructible.
  • Large Ham: He's a Game Show host. It comes with the territory.
  • Omnicidal Maniac: "Winner gets a brand new car! Loser gets their home planet destroyed!"
  • The Omnipotent/Reality Warper: Thanks to the matrix generators in his cuff links.
  • Time Abyss: Implied, as April states that his show has existed for eons.
  • Villainous Breakdown: Loses it when he discovers that his show is about to be destroyed.

    Zix, Travoltron, and Tee 
Voiced by: Maurice LaMarche (Zix), Jeff Bennett (Travoltron), Kevin Michael Richardson (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.
  • Armor-Piercing Question: After having a Heel–Face Turn 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)
  • Butt Monkey: 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 Heel–Face Turn.
  • Expy:
    • Tee is an alien who talks and acts like Mr. T.
    • Travoltron acts like John Travolta. Or at least his character in Saturday Night Fever. 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...
  • Good Feels Good: What Zix and Travoltron thought after helping Jimmy and friends, indicating that their Heel–Face Turn would be permanent.
  • Finger Gun: All three of them use this motion when shooting some kind of gooey substance used in sealing Jimmy's lab.
  • Heel–Face Turn: Tee during Jimmy and Sheen's imprisonment. Zix and Travoltron followed during the casts' time in Cretaceous Era.
  • Man Hug: Tee really likes to give this. Well, a bit too much. Travoltron too, to a lesser extent.
  • Real Men Hate Affection: In contrary to Tee and Travoltron, Zix hates Man Hug but he will accept a handshake with his teammates.
  • Speaks Fluent Animal: 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.
  • Verbal Tic: Tee tends to have "Fool!" in most of his sentence.

    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.
  • Brainy Baby: 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.
  • Bitch in Sheep's Clothing: His first appearance. Since his identity had been covered, he dropped the nice appearance in subsequent apearance.
  • Casanova Wannabe: Tried flirting with Beautiful Gorgeus with negative results.
  • Charlie Brown Baldness: Has one visible gravity-defying strand of hair only. Justified somehow that he's still a baby.
  • Cool Bike: 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.
  • Enfant Terrible: Duh.
  • Evil Genius: 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?
  • Evil Sounds Deep: He has a really deep voice, a clear contrast to his petite appearance.
  • Expy: He has several similarities with Stewie Griffin, both are baby geniuses with a rather unbabylike attitude.
  • Only Sane Man: Putting aside his need to change diapers, he's mostly this with King Goobot.
  • Running Gag: 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.

Alternative Title(s): The Adventures Of Jimmy Neutron