For characters from the original Jimmy Neutron: Boy Genius parent show, see here.
Sheen Estevez
Voiced by: Jeff Garcia
After disregarding a bunch of warning notes in Jimmy Neutron's lab, Sheen ends up piloting Jimmy's new rocket into space and crashing onto planet Zeenu, where he ends up praised by the inhabitants as a hero.- Character Exaggeration: Sheen used to be a nerdy, hyperactive kid in the old show, but here his redeeming qualities and serious traits have been erased, turning him into an obnoxious, self-centered moron.
- Idiot Hero: He's the main protagonist and is completely ditzy.
- Idiot Houdini: Sheen never gets punished for all the bad things he does and never gets called out on it.
- Insane Troll Logic: He forgets everything he used to know in the original series and now makes insane claims.
- Insufferable Imbecile: He is completely lacking in common sense and shows a gross disregard for the feelings of others.
- Never My Fault: He frequently blames Mr. Nesmith for the mistakes and misdeeds he makes.
- Nice Job Breaking It, Hero: He always puts Zeenu in danger. He is also the one who caused Dorkus to pursue him with never-ending vengeance. He stole Jimmy's rocket and back on Earth he's probably getting a lot of grief because of it?
- Took a Level in Dumbass: While he wasn't exactly Mensa material in Neutron, he's more idiotic here.
- Took a Level in Jerkass: While he could be a bit of jerk in the parent show, he still cared about his friends. Here, his positive traits are completely gone and his arrogance and selfishness have been cranked up.
- Unsympathetic Comedy Protagonist: His Flanderization puts him into this category perfectly.
Mr. Nesmith
Voiced by: Bob Joles
A chimpanzee from Earth who ended up on Zeenu after being sent into space and crosses paths with Sheen. He's more interested in fixing Sheen's rocket so they can go home, but his progress is often delayed by Sheen's antics.- Apes in Space: He was part of the space program and crash landed on Zeenu.
- Butt-Monkey: He frequently suffers because of Sheen's selfish and misguided decisions.
- Deadpan Snarker: He tends to make dry remarks about Sheen's dim-witted assumptions and ideas.
- Expy: He seems to be Jimmy if he was more responsible, patient, sensible and not-so irritable.
- Only Sane Man: He, Aseefa and Dorkus are often the most rational and realistic of the cast.
- Insistent Terminology: He often has to remind Sheen that he is a chimpanzee and not a monkey.
- Talking Animal: He is a talking chimpanzee.
Doppy Dopweiler
Voiced by: Rob Paulsen
A slug-like alien who looks like Carl and Sheen befriends after ending up on Zeenu.- Cowardly Sidekick: Just like Carl.
- Meaningful Name: Doppy's name is most likely a reference to him looking like Carl.
- Suspiciously Similar Substitute: He bears significant resemblance to Carl and even has the same voice. Sheen even is shocked by this when he first encounters him at the end of the pilot.
- Interestingly enough, Carl was going to be part of the show, but a Nick executive changed it to Doppy, Carl's alien double.
The Emperor
Voiced by: Fred Tatasciore
The ruler of Zeenu who blindly trusts Sheen with important tasks, unaware of the idiot the human really is.- Henpecked Husband: He is shown to be easily intimidated by his wife in "Nightmare Sheenario".
- Large Ham: He tends to speak loudly and with a lot of flare. Justified in that he is royalty.
- The Napoleon: He's much shorter than your average Zeenuian.
- The Noseless: It is mentioned in "QuaranSheen" that he used to have a nose, but removed it because of his extreme germophobia.
- Some Call Me "Tim": He is addressed as "The Emperor" because many people have trouble pronouncing his actual name.
- Top-Heavy Guy: He has a large chest and spindly legs.
Princess Oom
Voiced by: Candi Milo
The Emperor's daughter, who has a crush on Sheen, much to his dismay. She has a habit of licking him with her gigantic tongue, an action which she refers to as "raffenhoffering".- Abhorrent Admirer: Sheen is clearly not interested in her. The only reason he isn't upfront about disliking her is because he knows it might anger the Emperor.
- Affectionate Nickname: She's prone to calling Sheen "Sheeny-Weeny".
- All Love Is Unrequited: It never gets through Oom's thick skull that Sheen doesn't like her, no matter how many times he tells her.
- Brainless Beauty: One of her faces is beautiful. The other one is hideous.
- Genki Girl
- Huge Schoolgirl: She is extremely tall.
- Lecherous Licking: Her way of showing Sheen affection.
- Stalker with a Crush
- Two-Faced: She has two different faces, one that is somewhat attractive and one that is homely and has oversized lips.
Aseefa
Voiced by: Soleil Moon Frye
A warrior girl that Sheen becomes attracted to.- Action Girl
- Expy: Aseefa seems to take Libby's place as Sheen's significant other, but acts more like Betty or April.
- Gasshole: Aseefa becomes this after losing her roove in "Feeling Roovy". A roove is an animal living in Aseefa's throat that which enables her species to yodel. Without it, she belches constantly.
- Green-Skinned Space Babe: She's a very attractive girl with blue skin.
- Lady of War: She's very passionate about fighting.
- Only Sane Woman: She, Nesmith and Dorkus are the only rational and realistic characters of the show.
Dorkus Aurelius
Voiced by: Jeff Bennett
The main villain of the series. After Sheen accidentally destroyed his house in the pilot, Dorkus has ever since been hellbent on finding a way to get rid of Sheen or at least expose to the Emperor the moron Sheen really is.- Bald of Evil: When not wearing his hood, he is shown to be bald.
- Big Bad: He is the show's main antagonist.
- Butt-Monkey: Easily the biggest one in the show alongside Nesmith.
- Catchphrase: "Oh, grock."
- Expy: He acts a lot like King Goobot.
- Harmless Villain: More of the fact that all of his plans go up in flames. Even when it look like he succeeds, it never lasts long.
- Ineffectual Sympathetic Villain: None of his plans to get rid of Sheen work and he tends to suffer humiliating injuries because of them. Not to mention he was happy being The Emperor's #2 but everything literally came crashing down once Sheen arrived and took his position.
- In the Hood: He wears a shroud.
- Irony: Some of his more destructive schemes usually have the outcome of destroying his house when they backfire, which was one of the things Sheen did to Dorkus and why he has a grudge towards Sheen to begin with.
- Oh, Crap!: Prone to saying "Oh, grock" when he realizes something bad is about to happen to him.
- Only Sane Man: A very rare villain example as Dorkus doesn't take anything Sheen says or does for granted even saying he is a fraud. He also often tries to be the voice of reason for The Emperor but The Emperor would often side with Sheen at the end of the day.
- Unknown Rival: Sheen is completely oblivious that Dorkus hates him and wants to get rid of him.
- Villain Has a Point: Everything that Dorkus says about Sheen is 100% true but, of course in a show like this, nobody believes him.
Pinter
Voiced by: Thomas Lennon
Dorkus' main lackey, who is essentially a flying winged orange creature with one eyeball and a mouth.- Anti-Villain: Is only considered a "villain" because he is Dorkus' lackey. However, Pinter himself isn't evil at all.
- Cephalothorax: He's a head with limbs, but no body.
- Cyclops: He only has one eye.
- Elmuh Fudd Syndwome: He often pronounces L's and R's as W's.
- Expy: He seems to be one for Ooblar.
- Nice Guy: A fairly friendly character to both friend and foe alike.
- Number Two for Brains: He isn't much help to Dorkus, though he's usually more eccentric than outright stupid.
Bobb
Voiced by: Jeff Bennett
A minor recurring character in the series.- Defeat Means Friendship: He actually battled against Sheen in the pilot, but is shown to be on good terms with him in later episodes.
- My Nayme Is: His name is "Bob" spelled with three B's.
- Simpleton Voice: He has a moronic-sounding voice, which is similar to the voice Jeff Bennett used for Big Billy of the Gangreen Gang fom The Powerpuff Girls.
- Tiny-Headed Behemoth: He's a huge muscular guy, but his head is comically small.
