|Family||Hugh Neutron (Father), Judy Neutron (Mother), Granny Neutron (Paternal Grandmother), Baby Eddie (Cousin), Goddard (Pet), Newt Neutron (Uncle), Amanda Neutron Anabelle Neutron Kari Neutron Gomer Neutron|
|Friends||Carl Wheezer (Best Friend), Sheen Estevez (Best Friend), Cindy Vortex (Girlfriend and Future Wife), Libby Folfax|
|Likes||Science, Winning, Showing-off (sometimes), Cindy Vortex (But hides it), Betty Quinlan (Former Crush)|
|Dislikes||Being short, Made fun of, Cindy Vortex (sometimes)|
|Voice Actor||Debi Derryberry|
- "Gotta Blast!"
James Isaac "Jimmy "the Brain"" Neutron (born March 3) is the titular protagonist of the television series and the 2001 film. He is the world's smartest 11-year-old. He is named after scientists Sir Isaac Newton and James Chadwick (who was nicknamed "Jimmy Neutron" due to his discovery of the neutron).
Jimmy is a genius inventor, but his inventions seem to cause more destruction than anything good and it is usually up to him and his friends to stop them. He lives in Retroville with his robot dog, Goddard and his parents Hugh and Judy Neutron.
Jimmy has a disproportionately large head (which appears to be larger, due to his hair), blue eyes, and a large brown cowlick hairstyle. He is often teased because he is shorter than most boys of his age.
Jimmy's wardrobe consists almost exclusively of red T-shirts that sport his trademark symbol of electrons, circling a nucleus. He also wears blue jeans and a pair of grey and white Converse Chuck Taylor All-Stars. His underwear consists of plaid boxer shorts, as shown in the film and in the first episode of the series, he wears knee socks. In the shorts and the film, Jimmy wore blue shorts and brown shoes. He also wears his blue lab coat (and sometimes his welding mask while working on his inventions).
Jimmy has an I.Q. of 210, making him the smartest Retroville citizen. In a number of episodes, his classmates are annoyed and angered because Jimmy's brilliance renders trying to win projects and competitions things pointless. (In fact Jimmy has been banned for life from the science fair to give normal kids an actual chance). This brain, a source of constant comment, allows him to invent devices that accomplish even the impossible. That might seem like a gift to most people, but to Jimmy, it often causes him trouble. He designs his wild inventions to help him deal with bothersome chores, however the inventions tend to have a flaw (usually caused by an obvious oversight) which result in a catastrophe which only he can solve. He's rarely ever thanked however as people usually know he's the cause of the problem in the first place.
In the moment of crisis, he will urge his brain by saying, "Think, think, think!", where upon viewer enters Jimmy's ear and goes into his brain to observe its inner workings as well, as to relive a scene from the early part of the episode. Jimmy will then shout, "Brain Blast!", and arrive at the solution for whatever danger he has landed himself, his friends, or his town in. In the movie, he does not say "Think, think, think!" or "Brain Blast!" out loud, but says them in his mind. In the third season, he seems to stop brain blasting and comes up with ideas right away, with the exception being "Fundemonium".
Jimmy has a sweet personality, although sometimes he can be a bit arrogant. Jimmy is shown to be quite irritable around most people, the exception being his friends. He can be friendly at times, that he needs (or wants to be), but can come off as a smart-aleck or nerd occasionally. He enjoys playing the hero, often taking a staunch stand against anyone he believes to be evil. He won't back down from his beliefs as he strongly believes in himself. Jimmy is quite charming when he least tries to be, such as at the party, that he throws at his parents' absence in an early episode. He cares for his friends, family, and Retroville. It shows that Jimmy's intelligence is not inherited from the father, but he took it from his mother, conversely from his father Hugh, who is a "Duck-obsessed" adult.
However, he does have a few weaknesses; one of them is his poor communication skills. It takes him hours to explain things the "Science way" and people find his explanations very complicated and would ask for a shorter version of his story instead. Cindy calls him silver-tongued (in a sarcastic way), in the episode "Love Potion 976/J" as he finds it, which is accessible to him only, by means of a DNA scan from his hair.
Jimmy's inventions include Goddard, a time machine, and the Nanobots. He has several gum and candy-based inventions, which include The Neutronic Air Gum, that allow humans to breathe under water, gum that allows one to memorize books, and candy, that satisfies all the tongue's taste buds. After eating such candy, humans develop a physiological need (addiction) for it. He also made inventions to help him with transportation, the most frequently employed being his flying rocket or hover car. He also has a game pyramid, which allows players to go inside their favorite video game, and a Cloning Machine.
Jimmy also has a watch that is able to communicate with others, thought it is not clear when he invented (or enhanced) it.
One of his most recurring inventions is his Shrink Ray, which he uses to change the size of objects or people and the Chrono Arch, a time traveling machine.
In the video games, he makes several inventions, similar to the series. Many times, he creates different types of advanced spaceships with space buses, space bikes, being able to use amusement rides to create some, and finishing with his favorite, the hovercar, which he uses almost frequently. He creates these inventions in an extensive lab, located under his clubhouse, which is accessible to him only, by means of a DNA scan from a piece of his hair.
In the Chrysler Town & Country Commercial, he introduces his newest invention: "The Neutron Dimensionalizer."
The llama-obsessed Carl Wheezer is one of Jimmy's mutual friends. He may not be as smart as Jimmy, but he is very loyal to him. He's willing to help Jimmy as much as possible. Normally, he plays the foils to Jimmy's genius, and sometimes solve the episode's crisis with some innocent or insane observation. Other times, he merely cause the problem. He accompanies him in his wild adventures and end up in trouble.
Sheen is Jimmy's hyperactive friend who is obsessed with Ultralord. He is responsible for a great deal of the blunders Jimmy often has to fix. He also volunteers to test Jimmy's experiments, but not nearly as often as Carl. Like Carl, he is not as smart as Jimmy. Eventually, in Sheen's Brain, Jimmy uses the Brain Drain Helmet to make him a genius, which causes his brain to increase in size; he also gains telepathic abilities and telekinesis, though Jimmy is eventually able to reverse the effects. Trouble is never far away from Sheen, as is seen in several episodes of the show.Stranded." Examples of their closeness form the episode stranded:
- Cindy pushes Jimmy out of the way from being eaten by a giant plant
- Jimmy and Cindy both hug when their shivering in fear of the other dangerous plants
- Jimmy saves Cindy from a big snake.
- Jimmy holds Cindy's hand when they jump off the cliff into the oasis below
- They build an entire apartment-like hut right next to each other
- Cindy gives Jimmy a smoothie after he does a Tarzan-like jump into the oasis
- Cindy's vine broke, but luckily Jimmy caught her.
- Cindy and Jimmy hold hands together as they watch the sunset
In the Valentine's Day special, Jimmy is exposed with love potion and is in love with Cindy. He ends up asking Cindy to be his valentine and she reluctantly accepts. Jimmy and Cindy later become a couple after Jimmy kisses Cindy in "Lady sings the News."
Jimmy does not dislike Libby the way he shows it to Cindy Vortex in the beginning of the series due to her kindness towards boys. In Crouching Jimmy, Hidden Sheen, when Yoo-Yee kidnaps Libby, he works hard to help Sheen Estevez fight him to save her.
- Jimmy Neutron Vs. Cindy Vortex
- "Gotta blast!" - Jimmy's catchphrase
- "Think, think, think! Brain Blast!" - Jimmy's catchphrase
- "Very Capable Robots!"
- "I already told you Goddard, this invention helps me bring down my ego when Cindy calls me a 'know-it-all'. Which is pretty hard to do when you actually do know it ALL." - Substitute Creature
- "Twenty-five cents?! I'm worth at LEAST-" - Birth of a Salesman
- "Hmm... The candy is so perfect it seems to have developed a psychological need in people. Let the exploitation begin!!" - Krunch Time
- "I accept your nomination as mayor of Donkey Town." - Stranded
- "I'm sorry, miss. Do I know you?" - Normal Boy
- "Ha! Just kidding! Let's PARTY!!!" - The Eggpire Strikes Back
- "No, but we survived by learning to help each other, and that's what makes us rich: rich in friendship!" - A Beautiful Mine
- "(Goddard shows on screen)...Go back in time and tell Cindy you will lose the contest.' Jimmy: Goddard, whose side are you ON?!!..." - Birth of a Salesman
- "This is going to be a memorable Halloween Goddard. That is if we survive." - Nightmare in Retroville
- "That's a nice story, girls, but as it stands, I'M WINNING THIS CONTEST!!!" - Birth of a Salesman
- (Jimmy talking to Cindy) "I can't talk, I can't think. Everywhere I go, you're there!"
Cindy: "What kind of sick joke is this?"
Jimmy: "Oh, you're gonna make me say it, aren't you? Alright then, I'll say it..... I love you Cindy Vortex!" - Love Potion 976/J
- Jimmy: "I've developed a plan in case the ninjas return." - Crouching Jimmy, Hidden Sheen
- "I'm dead! I'm streaking, and I'm dead." - Jimmy Goes to College
- (Goddard shows on screen) "Cheating... Cheating would be dishonest." - Maximum Hugh
- "Gentlemen, I give you the Brain Drain 8000. The same dumbing down technology used by top radio personalities." - Normal Boy
- In the episode "Grumpy Young Men", he has a head similar to Albert Einstein.
- In the Japanese dub of the series, Jimmy is voiced by Ryouko Shiraishi.
- Throughout the show, it is constantly hinted at that Jimmy inherited his intelligence from his mother, who has shown certain degrees of brilliance herself like when in "See Jimmy Run", she explains how the overwhelming speed of the shoes could cause his shoes to meltdown. In fact, in the book Genius 101, he even comments on Judy's cleverness and Hugh's bumbling nature, saying that is quite obvious where he got his intellect. However, in "Clash of the Cousins", Jimmy analyzed the "Neutron genius gene" which actually comes from his father's side of the family. Although, it is a possibility that both sides of the family carry an individual genius gene.
- Jimmy Neutron makes an appearance in Bleedman's character chart with other familiar cartoon characters. He is seen wearing a Megaville elementary school uniform, it is revealed that he and his family had moved from Retroville to Megaville, the city that's in Bleedman's popular webcomic: PowerPuff Girls Doujinshi.
- He has an IQ of 210.
- In the pilot Runaway Rocketboy, he wears a striped shirt instead of the one with a drawing of an atom.
- Jimmy's name was originally Johnny Quasar.
- In Planet Sheen, he is only mentioned in the pilot.
- His hairstyle in Love Potion 976/J when dating Cindy resemble Eustace's.
- Jimmy is the only one on the show to appear nude in public.
- Jimmy is also the only character who does not act as an antagonist willingly.
- As an animation goof throughout the Jimmy Timmy Power Hour trilogy, whenever Jimmy is seen in 2D his watch constantly disappears off his wrist.
- Jimmy was inspired by Dexter from Dexter's Laboratory:
- Both are fond of science.
- Both are short.
- Both have mothers who are housewifes.
- Both have collectioner fathers.
- Both have pets for experiments.
- Both are fond of superheroes. Jimmy: Jet Fusion; Dexter: Major Glory
- But, unlike Dexter, Jimmy has lab rats friends and is an only child. Also, his parents are aware of his laboratory and his shenanigans (and so does most of Retroville), treating it much like daily life.