James Isaac "Jimmy" Neutron is a character also starring on Nickelodeon, who appears in the Jimmy Timmy Power Hour films. He has also appeared with Timmy Turner in a series of Nicktoon crossover video games starting with Nicktoons Unite! alongside SpongeBob SquarePants and fellow Butch Hartman creation Danny Phantom. As the star of the show The Adventures of Jimmy Neutron: Boy Genius, Jimmy is an adolescent whose genius inventions often get he and his friends in disastrous situations. He is voiced by Debi Derryberry.
In the first film of the trilogy, after Timmy brings his Auto-Poofer to Jimmy's lab, Jimmy is sent back to Timmy's room and believes Cosmo and Wanda are holograms. After spending much of the story using the Auto-Poofer, Jimmy adapts it to a game system and gives himself power to transport back to his home town of Retroville. Denzel Crocker steals the device and uses it to transport to Fairy World where he destroys The Big Wand and uses an arsenal of Fairy Weapons to change it into Crocker World. Convinced by Timmy that the Fairies need help and deserve to be protected, Jimmy poofs back to Dimsdale and uses the entries of Timmy's science fair to build a robot capable of fighting Crocker. Battling the robot with magic, Crocker discovers Cosmo and Wanda inside who were distracting him while the real Jimmy restored power to The Big Wand. With Fairy World saved, Timmy wishes for the two to return to their hometowns. Realizing Timmy is left with no time to compete in the science fair, Jimmy sends him his robotic dog Goddard as a thank you for saving him during his stay in Retroville.
Cosmo and Wanda's introduction to Jimmy is similar to their intro to Timmy in the pilot episode The Fairly Odd Parents!
Cosmo refers to Jimmy as "fudge-head" because of the shape of his hair and his hair's color.
In the first special, Timmy calls Jimmy "boy genius", a reference to the title of his series.
Jimmy is possibly the only human, without a fairy, that is aware of Cosmo and Wanda's existance as Timmy's fairies. However, Da Rules possibly only apply to humans that live in Timmy's world; so it can be implied that humans, as long as they live in different dimensions such as Jimmy's world, can be considered the only exceptions. Another possibility is that since Jimmy thinks they are computer programs, and not actually fairies, the rules haven't been violated.
Like Timmy, Jimmy Neutron is also voiced by a woman.