Nick is the second oldest of Jimmy's best friends, having to repeat fifth grade due to tardiness. He is one of the towns' wealthiest children, living in a 92-room mansion, with a bowling alley, maids' quarters, a screening room and a soda parlor. Nick enjoys giving advice to Jimmy and serves as a big brother towards him.
Nick has tan skin and styled black hair. He wears a blue jacket with a white shirt under it in the movie and the first season, though he changes into a black leather jacket in the second half of the second season and for the rest of the series (for unknown reasons). He does still have his old outfit in clipart, storybooks, video games, and merchandise, however. It is more remembered by fans. He wears a pair of dark blue hi-top Converse sneakers that matched his blue jacket. He also wears blue jeans in each of his appearances. He also wears a black string necklace with a gold ring tied to it around his neck.
Nick's personailty can best be described as pessimistic, arrogant, snarky and cynical, but deep down he is kind and compassionate. He can sing operatic German, which he only does secretly, as he thinks it is uncool. He can also style his hair without using his hands and is very vain about his hair, often flipping it around.
He sometimes breaks his leg due to reckless stunts on his skateboard and became known for his high-pitched scream that he lets out when this happens.
Nick and Sheen argue a lot because Nick finds Sheen annoying and immature, and the fact that Nick has a bad temper. Even though he may act like a jerk, Nick is kind and has a heart. He just doesn't want people to know that, since it would be bad for his reputation.
- "Dude, you're not a dude!!" -See Jimmy Run
- "Dude, my 'do is RUINED!!!" -Attack of the Twonkies
- "I'm gonna style my hair without using my hands. Can I get a drumroll, please?" -Broadcast Blues
- "Whatever, Neutron. But remember that there's only one opening night, and anybody who matters is gonna be there!" (skates into the alley) -Jimmy Neutron: Boy Genius
- "Augh, what's that smell?!" -Phantom of Retroland
- "Whoa! Check it out! Neutron has the moves!!" - Send in the Clones
- "Let me respond to that in the following way..." -Crime Sheen Investigation
- "I officially declare this party OVER... Out of my way, Shine!!" -Party at Neutron's
- "Augh!! I broke my leg!!" -My Big Fat Spy Wedding, Out, Darn Spotlight
- "Hey, Neutron. What did the Yokians give you?" -The Eggpire Strikes Back
- (mutters helplessly) "No more leeches, Mama! No more leeches, Mama! No more leeches, Mama!" -Journey to the Center of Carl
- "Why do I date rock stars? Because I can! (HONK!!!) Whoa! What have you done, Neutron?! I'm not beautiful anymore! Oh, wait... (holds up a mirror) Yeah, I am." (HONK!!!) -The Trouble with Clones
- "Why does this keep happening to me?!" -League of Villains
- "You know, these are as cool as...me!" -Krunch Time
- "Well, let's think about that, Sheen... Maybe sit on the shelf because HE'S A DOLL?!"-Jimmy Neutron: Boy Genius
- "Hey, watch it, Neutron!" -Out, Darn Spotlight
- "Oh, my God! You are such a baby!" -Jimmy Neutron: Boy Genius
- "An anti-gravity skateboard! Thanks, creepy alien dudes!" -The Eggpire Strikes Back
- "I never said that!" -Crime Sheen Investigation
- "Like me?" -Professor Calamitous, I Presume
- "Okay, I will." -The Eggpire Strikes Back
- "Everyone knows about the Phantom. He wears a long black cape, he has a log of salami for a right leg, and he stalks the park after dark, looking for victims to eat!" -The Phantom of Retroland
- "Parents!? What, are you guys gonna be kids forever!?" -Jimmy Neutron: Boy Genius
- "Just think, if you bone-headed dweebs had listened to your parents, you'd be home in bed instead of riding this monster!" -Jimmy Neutron: Boy Genius
- "He busted my skateboard dude!" -Send in the Clones
- Jimmy always ends up in trouble when he takes Nick's advice.
- A running gag is that he breaks his leg from time to time due to reckless stunts, usually on his skateboard, leading some fans to speculate about the possibility of him having a permanent limp or knee injury later in life. It was revealed in The League of Villains that Nick has lost his coolness, due to him always breaking his leg.
- While Nick had a fairly large role in the movie and season one, he was reduced to a secondary character for the rest of the series. He was going to rejoin the main cast in season four, however and would've continued to develop his character and his relationships with Jimmy and the gang.
- One theory of why Nick lost his main character status is that Libby took his place, and she starts be used more and more.
- Another reason Nick lost his status as a main character was because doing Nick's voice would sometimes strain Candi Milo's vocal chords.
- Jimmy and Nick are the only male characters to be voiced by a woman. Jimmy is voiced by Debi Derryberry and Nick is voiced by Candi Milo.
- Nick and Betty playing Macbeth and Lady Macbeth could've been a reference to the fact that Jimmy and Cindy both have had crushes on them. It could also hint romantic chemistry between them.
- In the movie, he was always holding a purple lollipop, but this was later removed in the show, with the exception being The Eggpire Strikes Back.
- He probably wears briefs, as seen in The Trouble with Clones, where his evil clone was given a wedgie.
- Aside from Butch, Nick is the only character in the franchise who never refers to Jimmy by his first name, as Nick only refers to him as "Neutron", "Nerd Bomb" or "Boy Wonder". Although he does use Jimmy's first name in a few storybooks and in Make Room for Daddy-O.
- In the film, when the children reunite with their parents, Nick is shown with just a mother. This makes Nick the only one of Jimmy's best friends not to have a father. He is also one of the two characters we know who has a single parent. The other one is Sheen.
- A running gag in the series is that Nick often forgets Sheen's name, no matter how many times he tells him to which he usually replies with a "Whatever", implying he doesn't care about names or he might be anti-social.
- Nick's last name is a reference to James Dean, who is best known for playing similar "bad boy" roles.
- Many of the times he has broken his leg have been because of repeated tries to jump a fire hydrant while skateboarding. He should stop doing that.
- Cindy had a crush on Nick in the movie and early episodes and would often try to get his attention, but Jimmy kept ruining her chances with him due to his endless pranks. Her chances were ruined once and for all in Trading Faces when Jimmy made Cindy look like a fool in front of Nick. Nick and Cindy do remain friends, however.
- Originally, Nick was going to be black and more of a basketball jock, but he was changed to Brazilian and more of a bad boy. He and Libby were also going to be cousins.
- In the movie, his voice was more scratchy and high pitched, but in the show, his voice is a bit more deep and clear. His voice in the show also sounds like Revvin' Evan the Fire Engine on the PBS Kids show, Jay Jay the Jet Plane, one show that Jimmy's voice actor, Debi Derryberry, used to be in, voicing the titular character
- His Planet Sheen counterpart is Grish.
- Nick has a list of all the girls he has kissed.
- In the movie, Nick was more of a bully to Jimmy and his friends, but when the show began, he became much kinder towards them.
Villains: King Goobot V | Professor Calamitous | Eustace Strych | Beautiful Gorgeous | Meldar Prime | Evil Jimmy | The Junkman | Zix, Travoltron and Tee | Baby Eddie | Gortox the Irritable | Dr. Sydney Moist