Aki is a girl who sits next to Dib. She has dark reddish hair with a widow's peak. She is classed as one of the "popular kids" at Skool, shown in "Bestest Friend". Voiced by Antoinette Spolar.
Alex is a dark-haired girl with squinty eyes (like Gaz) who attends Ms. Bitters' class and can be seen in the background in "The Nightmare Begins", "Bestest Friend", "Career Day" and other episodes that are set in the Skool.
Brian sat right next to Zim, and probably had the most lines out of the Skoolchildren. He also appears in "Vindicated!", getting bored and walking away before a dodgeball hits Zim.
Because Ms. Bitters was getting tired of him, Brian was sent to the "Underground Classes" in "Tak: The Hideous New Girl", implying that he died since he never returned (and also because in the commentary Jhonen said he was glad to be done with him).
A much smaller child resembling Brian appears in a crowd in "The Most Horrible X-Mas Ever". He appears in "Bolognius Maximus", mocking Zim, calling him "bologna-boy". Brian was replaced by "Poonchy, Drinker of Hate". He was voiced by Jhonen Vasquez, and his design was based on art director Bryan Konietzko.
Carl wears a red stocking cap that covers his eyes. He mentioned that he left his underpants on for a month in "Bolognius Maximus". In "Lice", he was infested so badly that he scratched through his cap, hair and scalp, down to his bare skull. He also gave Melvin a wedgie in "Tak: The Hideous New Girl". Carl was voiced by Jhonen Vasquez just like Brian.
Chunk is one of the bullies that torments Dib, and occasionally Zim. He has orange hair, a thick red jacket and drools a lot. He likes dogs, as shown in "A Room with a Moose", which contains his largest speaking role. In "Dark Harvest", he threw a ball at Zootch during recess, injuring his spleen. Chunk was voiced by Adam Paul.
Davey Gutzmann is a 2nd grader at Skool that won the Skool's talent show in Issue 10. He is a short, chubby kid with trim cut black hair. He wears a light blue shirt and purple pants, and carries a boa constrictor named Commander Squeezers with him. Zim and Dib are both upset that he won the talent show, since having a pet snake isn't really a talent.
Dirge is one of the kids at the "rejects" table in the corner of the cafeteria (along with Keef, Gretchen, and Matthew P. Mathers III), as shown in "Bestest Friend". He has dark skin and wears a green skull T-shirt.
He seems proud of his deformity (webbed toes) which he describes as "like some kind of horrible fish-boy", but everybody gets creeped out when he offers to show it to them. He is sometimes known as "Pooka" in the storyboards. He is probably named after Roman Dirge. He was voiced by Danny Cooksey.
Flan is the kid who has cyan hair and freckles. He makes several cameo appearances, though most notably in "A Room with a Moose"; when GIR calls up several Skoolchildren up to go on a "field trip", Flan is one of them. He was voiced by Adam Paul.
Francine is a blonde girl who is in Gaz's class.
Gretchen has purple hair, big upper teeth and braces. In "Bestest Friend" she is among the losers in the corner (with Keef, Dirge and Matthew P. Mathers III) and mentions that she has never been to a party. In "Lice" (which contains her largest speaking role), she made inane comments while being dragged around by Countess von Verminstrasser, the Delouser.
In "Halloween Spectacular of Spooky Doom" her nightmare self had a grotesquely large mouth with many large, pointed teeth. In "Tak: The Hideous New Girl" we discover that she has a crush on Dib; she gives him a stack of heart-shaped steaks and weeps when he is talking with Tak. In the second episode, "Bestest Friend", she was shown not to be absorbant as well as other things, and failed Zim's best friend test. She was voiced by Annoinette Spolar.
Jessica isn't in Dib or Gaz's class, but she appears often enough regardless, notably in "A Room with a Moose", "Bestest Friend" and "The Voting of the Doomed". She is one of the stereotypical popular kids who thinks lowly of Zim, Dib, and the rejects. Like Gaz, she usually has her eyes slightly shut or squinting. Her hair is blonde. She was voiced by Antoinette Spolar.
In "Bestest Friend", Keef survives Zim's rigorous testing and is declared his "best friend". He then begins stalking Zim obsessively, until Zim finally replaces his eyes with mechanical ones that allow him a degree of hypnotic mind control, making him believe the next living thing he sees is Zim.
This leads to him seeing a squirrel as Zim and he ultimately falls off of a house. The ending makes it look as if he died, though he reappears in a few other episodes and was supposed to have a big role in the episode "Return of Keef", where he was supposed to die again, but didn't. He was voiced by Danny Cooksey.
Letty is a dark-blue-haired girl with a purple sleeveless shirt and a spotted dark blue skirt. She usually has her eyes closed or squinting like Gaz. She is seen playing in the rain with Margie and Tae in "The Wettening". Like Jessica and Penny, her long hair curls backwards instead of forwards.
Lizard Boy is arguably the most recognizable background character, but seen in only a short selection of episodes. Lizard Boy has one very interesting talent: By holding a drinking glass in his mouth, Lizard Boy can wiggle his tongue in his mouth while making a strange squeaking sound, which he demonstrated to a student in "Parent Teacher Night".
Melvin gave a presentation during the Pilot. He ate paste in "The Wettening", and was handcuffed to Dib after starting a lice infestation in the episode "Lice". His head floated off for a while after declaring that he wanted to be an astronaut in "Career Day". He was also sitting at the rejects' table in "Bestest Friend". He was originally voiced by Hope Levy in the Pilot, but it was later decided that Danny Cooksey would be Melvin's voice actor.Halloween Spectacular of Spooky Doom".
She was also among the students Zim imagined as horrific monsters. Her father was possibly Officer Squidman, as a picture of her (or at least a child that looks a lot like her) appeared in his wallet right below a picture of his other children in the episode "GIR Goes Crazy and Stuff".
In "FBI Warning of Doom", she could be seen at the rental store being harassed by the stressed-out employee, and in "Walk for Your Lives", she was led away from the slow-motion explosion by what appears to be her grandmother. She was also experimented on by Zim in "The Frycook What Came from All That Space" until he shoved her off his desk and resumed pretending to be a human. She also left and took a nap during the dodgeball scene in "Vindicated!". She was shown multiple times not to wear any kind of pants or underpants. She was voiced by Antonette Spolar.
Matthew P. Mathers III
Matthew is a cowardly boy that Zim dubbed a "squeally fool" when he ran away screaming after Zim asked him to be his friend in "Bestest Friend". He has pale-colored skin but is sometimes seen with normal skin. He was also seen with Carl dragging along with him in the hallway in "Dark Harvest". Matthew was voiced by Danny Cooksey.
Nub Bubbins is a small child with nubby arms and legs. He can be seen being read a "Pig Girl" story in "Gaz, Taster of Pork". More notably, he might be another alien in disguise, as he is seen to have an alien doppelganger in "Hobo 13", which he can be seen dressed as in "Halloween Spectacular of Spooky Doom" as GIR was attacking trick-or-treaters.
Old Kid looks like an elderly adult in a kid's body. He sits at the very back of the classroom. This character is actually based upon Don Newhouse, the security guard at the front gate of Nickelodeon Studios (who also appears in the SpongeBob episode "Mermaid Man and Barnacle Boy") as told in the commentary. He has a small speaking role in "The Nightmare Begins", and appears in "Career Day" as a fan of Count Cocofang. Old Kid was voiced by Jhonen Vasquez.
Peyoopi is the girl with green hair in cone-shaped pigtails. She wears lipstick the same color as her hair, a pinkish dress, and stripy stockings, and often has a vacant-looking smile on her face. Like most of the other Skoolchildren, she loves the rain for whatever reason. She was placed under Zim's mind control in "Rise of the Zitboy". She was voiced by Antoinette Spolar.
A brunette girl with freckles, she attends Miss Bitters' class at the Skool. Her biggest role came in Issue 15 of the comic series, where she tells one of the four stories about possible origins of Miss Bitters.
Pig Boy is a pig student who, during "The Frycook What Came from All That Space" jumped out a window and flies away, gravely insulted, when Dib declared that Zim's description of humans as "pig smellies" is offensive. Zita attempted to comfort Pig Boy, angrily telling Dib to watch what he says around him, and then everyone got mad at him for saying that. Pig Boy was never seen again, but was voiced by Rosearik Rikki Simons.
Pinky is a boy who appeared in "Vindicated!", where he was seen to have a bad case of pinkeye. After Zim said that he had a case of the disease to cover up the loss of one of his contacts, Zita said "Yeah, Pinky's got it bad." According to Vasquez and concept art, the boy's real name is "Scarball".
Poonchy has orange hair and is often seen with his hands in the air. He wears a sporty outfit with a headband, and loosely resembles fitness guru Richard Simmons. He replaced Brian in "Tak: The Hideous New Girl", walking to his new seat with his hands in the air and turning all around to make sure people noticed that he was there, and in "Dibship Rising" he mocked the Dibship, but didn't seem to realize that it wasn't Dib.
He was to have a major role in the unfinished episode "Invader Poonchy". In Enter the Florpus, Minimoose steals a pizza sticker off of Poonchy’s mom’s car, despite Poonchy repeatedly begging him to stop. Poonchy was voiced by Paul Greenberg.
Rob has two orange tufts of hair which look like horns. He gave Dib a severe, funk-accompanied wedgie on the bus in "A Room with a Moose". While being interviewed in "Mysterious Mysteries", Rob tearfully denied Dib's claim that his dad is a yeti.
In "Tak: The Hideous New Girl", Rob was transferred to the "underground classrooms", but later returned after Tak flees. Rob's design was based on writer Rob Hummel, and he was voiced by Adam Paul.
Sara is, in most respects, a very typical example of your average Skoolchild; that is to say rude, judgmental, and overall unintelligent. She has long blue hair, large green eyes, a thin unibrow, and dark circles under her eyes. She was voiced by Janice Kawaye.
Spoo is a boy with red hair, beady bluish-green eyes with what seem to have only irises, pointy nose, and a green shirt. His organ was stolen and replaced with Dib's heat radiator hall pass in "Dark Harvest". He was destined to a fate of being a veterinarian in "Career Day", despite his apparent animal allergy. Spoo was voiced by Adam Paul, and Antoinette Spolar on one occasion.
Spork is a skool kid who shares his name with a former Almighty Tallest. Not much else is known about him, since he never made an official appearance.
Tae was the kid in "The Nightmare Begins" who told Dib that just because somebody looks different doesn't mean they are an alien and that Old Kid would be a alien too if it was like that. He has blue hair and freckles.
He played a small role in the beginning of the "Pilot" when Dib tells him the new kid is an alien and then he responds "What new kid? You're crazy." He was voiced by Kevin McDonald.
The letter M is a boy who seems to agree that Zim is weirder than most of the other kids, but still doesn't think he's an alien like Dib says. He sits between Brian and Dib.
He is called "The Letter M" in both the credits and by the other students (or at least by Zita in "Halloween Spectacular of Spooky Doom"), and is never referred to by any other name. It seems to be a reference to the shape of his face with his pronounced widow's peak, which gives his hairline an M-like shape. He was voiced by Phil Lamarr.
The skool president is a disturbingly effervescent girl who suffered a mysteriously-induced seizure immediately after complaining about the dirty Skool bathrooms at a pep rally in "The Voting of the Doomed".
She is whisked away by riot-gear-equipped Skool security, and an election for a new student president is held in which Willy triumphs over Zim. As of now her fate is unknown, as is what the Skool security did to her afterward. She was voiced by Kathryn Fiore.
Torque is a skoolchild only interested in sports and weightlifting. Torque wears a jersey with his name on it. Dib tries to protect Torque in "Dark Harvest", and in that episode Torque seems remarkably tolerant of Dib's weirdness. In the unfinished episode "Ten Minutes to Doom", Torque starts to hate Zim because Dib said Zim called him a dookieweenie. Torque was voiced by Jason Marsden.
Deemed "leadership material" by the skool, but considered a bald, drooling moron by everyone else. In "Bolognius Maximus", he was the last person to use the toilet before Ms. Bitters ordered Dib to roll around in it until he smelled better. In "The Voting of the Doomed", Willy was elected class president with Dib's help, then brainwashed by the mysterious principal, making him act more intelligent and speak with a British accent. Willy was voiced by Jim Wise.
Zita is a skoolchild who sits behind Zim and like most of the skoolchildren, Zita considers Dib to be crazy. Strangely, Ms. Bitters seems to have taken a liking to her and Zita returns the respect. She has purple spiky hair with a headband, brown eyes, and a sleeveless black-and-lavender dress. Zita was voiced by Mo Collins.
Zooglodon is the kid who got hit with a tetherball when Zim used Keef to whack it back in the episode "Bestest Friend".
Zootch is a kid who got hit by a dodgeball thrown by Chunk in "Dark Harvest". His most defining characteristic is the single spike of hair in the center of his head. He might be another alien in disguise, given both his strange name, (even for the show) and that he is seen to have an alien doppelganger in "Hobo 13". He is in Gaz's class, as seen in "Gaz, Taster of Pork". Strangely, however, he is also seen walking out of Ms. Bitters' class in "Career Day". He was voiced by Jason Marsden.