Main •
Fanboy (voiced by
David Hornsby) is an enthusiastic fan of
comic books,
fantasy,
science fiction and
action figures. •
Chum Chum (voiced by
Nika Futterman and
Nancy Cartwright in the pilot from
Random! Cartoons) is Fanboy's best friend and sidekick. Although he is younger than the other main characters, he is still in the same class as them. Show creator Eric Robles explained on the Nickelodeon message board that this is because Fanboy snuck him into his class and the teacher never noticed the age difference. Chum Chum is incredibly loyal, sweet, playful, energetic, emotionally mature and high-spirited.
Supporting •
Kyle Bloodworth-Thomason (voiced by
Jamie Kennedy) is an insecure pre-teen wizard who loathes Fanboy and Chum Chum, but secretly enjoys their friendship. Kyle was expelled from his wizarding school, Milkweed Academy, for turning his teacher Professor Flan into a raspberry
flan. Kyle is now reluctantly enrolled in Fanboy and Chum Chum's public school, where he has very few friends other than Fanboy and Chum Chum. As Kyle struggles to be re-admitted to Milkweed, he often suffers painful indignities. •
Ozwald "Oz" Harmounian (voiced by
Josh Duhamel) is the owner of the local comic shop, Oz Comix. Oz is a friend of the boys, who consider him "the most knowledgeable human being ever", though he is a nerdish know-it-all who lives with his elderly mother. •
Leonard "Lenny" Flynn-Boyle (voiced by
Wyatt Cenac) is the accident-prone junior manager of the Frosty Mart (a parody of
7-Eleven). He finds Fanboy and Chum Chum irritating and sometimes gets a "stress twitch" when annoyed by them. •
Boogregard "Boog" Shlizetti (voiced by
Jeff Bennett) is a short-tempered bully who likes to "bop" people and is obsessed with the video game
Chimp Chomp (a parody of
Donkey Kong). Boog's voice is a parody of
John Travolta's character Vinnie Barbarino from
Welcome Back, Kotter. •
Mr. Hank Mufflin (voiced by Jeff Bennett) is Fanboy and Chum Chum's grouchy yet often playful teacher. •
Yo (voiced by
Dyana Liu) is another of Fanboy and Chum Chum's classmates. She is happy-go-lucky and loves her Yamaguchi (a parody of
Tamagotchi) digital pets, especially Scampers, a cat Yamaguchi. She has a rather insane crush on Chum Chum, and often wants to play with him like he's a toy. Though she can be overly obsessive, she is normally nice. •
Lupe (voiced by
Candi Milo) is a kind-spirited girl in Fanboy and Chum Chum's class. Lupe appears to be Yo's friend, and the two are often seen together. •
Dollar-nator (voiced by Jeff Bennett) is a Jamaican-accented artificial intelligence built by Fanboy in the future and sent back in time to bail the present-day Fanboy and Chum Chum out of a jam. He is a parody of the
Terminator. •
Janitor Russ Poopatine (voiced by
Steve Tompkins) is a janitor at Fanboy and Chum Chum's school. He is a parody of
Emperor Palpatine from
Star Wars. He is a pale, skinny, gnarled old man who wears a dark hooded shirt. Poopatine rides around in a sentient cart named Brenda. Brenda solely communicates in robotic noises, which Poopatine is capable of understanding. •
Man-Arctica (voiced by Jeff Bennett) is an ice-based superhero who scours the cosmos looking for scofflaws. Man-Arctica balances a mild disdain for humanity against his duty to save them from harm. Man-Arctica was asked to become president, but he declined due to the heavy responsibilities. •
Agent Johnson (voiced by Jeff Bennett) is the do-it-all authority figure in Galaxy Hills. •
Chris Chuggy (voiced by Eric Robles) is a classmate of Fanboy and Chum Chum's who communicates only by saying "Wah". •
Michael Johnson (voiced by Wyatt Cenac) is a classmate of Fanboy and Chum Chum's. His name and clothing is a parody of
Michael Jackson as he is depicted as a good dancer and gets around by
moonwalking. •
Duke (voiced by David Graham) is a classmate of Fanboy and Chum Chum's. •
Cher "Cheer" Leader is a cheerleader in Mr. Mufflin's class. She is a triplet and sometimes appears with her 2 other cheerleader sisters, who look exactly like her. The triplets were voiced by Kari Wahlgren in "Fanboy Stinks", but Cher is voiced by Candi Milo in all other appearances. •
Nancy Pancy (voiced by
Kari Wahlgren; in "Fanboy A'hoy!" and "Slime Day", and by Nika Futterman) is a sweet and mature girl in Mr. Mufflin's class. •
Francine is a brown-haired
diva in Mr. Mufflin's class. Voiced by Candi Milo. •
Cheech is a classmate in Mr. Mufflin's classroom. In "The Janitor Strikes Back" he was voiced by Nika Futterman. •
Fankylechum (voiced by Jamie Kennedy) is a nerdy, good-spirited classmate of the boys. •
Lunch Lady Cram (voiced by Candi Milo) is the new strict
lunch lady who replaced the former strict lunch lady, Mildred. She is known for making glop. •
Ms. Harmounian (voiced by
Estelle Harris) is a single mother committed to teaching her adult son, Oz, that the only way to run a successful business is by selling. •
Scrivener Elf (voiced by Jeff Bennett) is an
elf Kyle creates in "The Janitor Strikes Back" to do his homework and other tasks, but he appears other times in the series as well. •
Necronomicon (voiced by Jeff Bennett) is a talking
book of spells who is a companion to Kyle, and nags him about the moral implications of his choices. •
Sigmund The Sorcerer (voiced by Jeff Bennett) is Kyle's more successful and skillful German wizard rival from Kyle's former school for wizards, Milkweed Academy. •
Fedora Man (voiced by Jeff Bennett) is one of the delivery people in Galaxy Hills. •
Secret Shopper (voiced by Jeff Bennett) first appeared to evaluate Frosty Mart product quality and customer service in "Secret Shopper". •
Dirty Bird is a seagull who makes cameos throughout the show. •
Thorvald the Red (voiced by
Nolan North) is a
Viking hero who debuted first in "Norse-ing Around" and in "Norse Code" and in "The Last Strawberry Fun Finger" debuted last in "Normal Day". •
The Global Warmer (voiced by David Graham) is a supervillain and archenemy of Man-Arctica who appears several times in the series. •
Henry Harmounian (voiced by
Dick Van Dyke) is an optimistic, hardworking, cunning and whip-smart father who helps vast knowledge to teaching comic books with his son, Oz and brings wealth to its own. •
Mitzi is Oz's mom's pet goat. She uses Mitzi to make milk, and in "The Hard Sell", she was to turn Oz's shop into a yogurt shop using yogurt created from Mitzi's milk. He is voiced by David Hornsby in "The Winners". •
Professor Flan (voiced by
Jim Cummings) is a professor from Milkweed Academy whose permission Kyle has to grant to re-admit to Milkweed. He is the one who Kyle turned into a raspberry flan. •
Brizwald Harmounian (voiced by Amir Talai) is Oz's money-loving, scheming cousin. •
Chimp Chomp is a
Donkey Kong parody video game featuring a monkey, Chimp Chomp, who is trying to take an ape's bananas. Boog is addicted to the video game. The game is playable on Nick.com. •
Precious (voiced by
Dee Bradley Baker) is Mr. Mufflin's class pig. Precious appears in "Precious Pig" but a look-alike pig that could be Precious appeared in "Eyes on the Prize" and "Fanboy A'Hoy!" •
Berry (voiced by
Kevin Michael Richardson) is a small pink creature who lives inside the Frosty Freezy Freeze machine at the Frosty Mart. •
The Ice Monster (voiced by Kevin Michael Richardson) is a frighteningly large beast created from the combination of Frosty Freezy Freeze and Ice-Monster Bun Bun, in the pilot episode from
Random! Cartoons. It reappears in "Brain Freeze" when Blue-Tonium and Radioactive Red Frosty Freezy Freeze combine. •
Dr. Acula (voiced by David Graham) is a
vampire plastic surgeon. He inadvertently transforms Fanboy into a vampire and attempts to have him bite Chum Chum to transform him as well, but is destroyed by sunlight. •
Miss Olive (voiced by Candi Milo) is a preschool teacher. •
Marsha (voiced by Candi Milo) was a sweet, successful student until Fanboy accidentally ruined her life by sneezing on her placement test, rendering it illegible. As a result, she received a failing grade and had to repeat kindergarten, causing her to swear revenge on Fanboy. •
Fanbot is a robotic version of Fanboy that appears in "I, Fanbot". •
Mecha-Tech (voiced by Dee Bradley Baker) is a dancing, robot action figure. Mecha-Tech often says, "I await your command!" and can do anything its owner tells it to do. •
Monster in the Mist (voiced by Jeff Bennett) is a figment of Boog's imagination. •
Scampers (voiced by Dee Bradley Baker) is Yo's cat Yamaguchi. •
Yum Yum (voiced by
John DiMaggio) is a cycloptic bubblegum creature created by Fanboy and Chum Chum in "The Janitor Strikes Back". •
Fanman (voiced by
Scott Grimes) is a superhero who appeared in the
Random! Cartoons short "Fanboy". •
Sprinkles (voiced by Dee Bradley Baker) is the class bear. •
Muk Muk (voiced by Nika Futterman) is a female, semi-feral cousin of Chum Chum who hails from West Apetown. •
Crabulus: Destroyer of Worlds (voiced by Jeff Bennett) is a crab-like action figure. He appears several times in the series and is portrayed as being unpopular with collectors due to his embarrassing exercise DVD. •
Moppy is a mop that Fanboy assembled as a date for his school dance in "Moppy Dearest". •
Agent 08 is an octopus cartoon character of whom Fanboy and Chum Chum are big fans. Agent 08 is notorious for being made into a dangerous and explosive collectible toy which Oz owned and hid because it was supposed to be discontinued. •
The Burgle Brats are three kindergartners with propensities for crime. •
Stinks is a dirt-based creature who takes over Fanboy's right glove and forces him to commit crimes. •
Nurse Lady Pam is a school nurse who is in love with Man-Arctica. Fanboy and Chum Chum fight for her attention in "Lice, Lice, Baby". ==Broadcast==