James Isaac "Jimmy" Neutron (born March 3) is the title character and the main protagonist of the television series and the 2001 movie. 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", because of 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, who is named after Robert H. Goddard (a pioneer in modern rocketry) and his parents, Hugh Neutron, a bumbling used car salesman and duck-lover, and his caring housewife mother 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. n 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.
It is not said when Jimmy invented or (enhanced his watch) but he had a watch that is able to communicate with others
One of his most recurring inventions is his shrink ray, which he uses to change the size of objects or people; 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 Dimmensioniliz."
- 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.
- Jimmy is also the only character who does not act as an antagonist willingly.
- 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.
- Jimmy Neutron was voiced by Debi Derryberry.
- Jimmy Nuetron will meet Thomas, Twilight, and their friends in Thomas and Twilight's Adventure with Jimmy Neutron: Boy Genius.