Characters: My Gym Partner's A Monkey
Voiced by: Nika FuttermanA human boy who was transferred from Chester Arthur Middle School to Charles Darwin Middle School by an accidental misspelling of his last name from "Lyon" to "Lion".
- Asshole Victim: In Hyena And The Mighty, after Adam is being uncharacteristically mean to poor old Rufus, he gets injured by random machines in a stunt. But you can't feel bad for him for being a jerk to Rufus.
- Body Horror: At the end of Hyena and the Mighty, Adam gets beat up by random machines after threatening Rufus to stop crying and Adam's beating makes Rufus laugh and results in Adam getting injured and bruised. But he deserved it for the massive jerk he was being.
- Butt Monkey
- The Chew Toy
- Deadpan Snarker
- Failure Hero: Most of the time.
- The Hero: The closest this show has to one.
- Jerkass Ball: The Hyena And The Mighty.
- Jumping Off the Slippery Slope: The Hyena And The Mighty. His abuse of Rufus Hyena. Particularly the scene where he threatens the hyena with physical violence to stop crying.
- Kick the Son of a Bitch: See Body Horror above.
- The Napoleon: He's in middle school and is short and stout.
- Only Sane Man: Literally.
- Stranger in a Strange School: A human boy accidentally sent to an animal school.
- Token Human
- Youthful Freckles
Voiced by: Tom KennyA spider monkey who quickly became Adam's best friend. He is often very possessive of Adam and hates not having him around regularly. Jake is emotional and goofy who takes to heart some of Adam's comments and actions, leading to some overly dramatic and exaggerated reactions. He can be lazy and selfish, but at the same time he is also fairly sensible.
- Ambiguously Gay: Has some shades of this
- Clingy Jealous Guy
- Everything's Better with Monkeys
- Idiot Houdini:: Usually when he causes mischief, Adam gets the blame.
- Jerk Ass
- Jerk with a Heart of Gold
- The Lancer
- Large Ham
- Never My Fault
- Running Gag: His obsession with his own butt.
- With Friends Like These...
Voiced by: Rick GomezA highly intelligent lowland gorilla who serves as the anti-bully at the school and often gives confusing wisdom to people. He speaks in a soft-spoken and nearly monotonous manner, often stringing together technical words as a matter of his normal speech.
- Ambiguously Gay: In The Hyena And The Mighty, he calls Rufus Hyena his sweet, implying the two may be in a relationship despite Rufus being a one shot character. However, later, he was seen being attracted to another female gorrila
- The Big Guy
- Deadpan Snarker
- Genius Bruiser: He's both intelligent and powerful.
- Gentle Giant: Despite his massive physique, he's capable of taking care of a baby for a school project.
- Break the Cutie: Quite a few episodes do this to her.
- The Chick
- Cute Clumsy Girl
- Clingy Jealous Girl: She tries to break up Kerry and Adam more thann once.
- Dogged Nice Girl: To Adam.
- Huge Schoolgirl: The tallest character in the show (her head is out of the screen most of the time).
- Shrinking Violet
- Stalker with a Crush: To Adam of all people.
Voiced by: Rick GomezAn easy-going, street-talking green tree python. He is an underachiever and excessive daydreamer who's gullibility allows him to believe anything he hears, which makes him a constant source of misinformation.
- Cloud Cuckoo Lander: His antics and personality make him border one being one
- The Ditz: Moreso the anyone else in the show.
- The Heart
- Reptiles Are Abhorrent: Averted. He's actually a pretty decent guy.
- Surfer Dude: Talks like this.
- The Stoner: Acts like one
Guadalupe "Lupe" Toucan
Virgil "Bull" Sharkowski
- Always Someone Better: His big sister is a way better bully than he'll ever be. He's extremely sensitive about this fact. Especially so when she managed to teach Adam to go frenzy in minutes though trolling. A concept he himself spent the whole episode trying to teach the ever oblivious Adam to no avail.
- The Bully: At least until his big sister comes in.
- Mobile Fishbowl: Wears a special headset over his gills to breathe while on dry land.
- Only Known by Their Nickname: He's mostly called "Bull"
- Verbal Tic: Takes a deep breath between his words every once in a while.
Voiced by: Tom KennyA nine-banded armadillo with a Texas accent and a reporter in the school media.
- American Accents: Southern
- Nerd Glasses
- Too Kinky to Torture: He seems to like everyone treating him like crap.
- Hollywood Nerd
- Insufferable Genius
- The Leader: Of his fellow nerds: a pig, an elephant, an octopus, and a parrot.
- Nonindicative Name: Though Phineas Dolphin doesn't quite have the same roll off the tongue.
Margaret Rhino, Joanna Buffalo, and LeTanya HippoA trio consisting of a Sumatran rhino, cape buffalo, and hippopotamus.
- Big Beautiful Woman and Brainless Beauty
- Big Eater: All three.
- Valley Girl: Joanna
- Sassy Black Girl: LeTanya
James AntA red ant.
Endugu ElephantA Jamaican-American African Elephant
Principal Poncherello Pegone Pixiefrog
- Bunny-Ears Lawyer: Although not very bright, he has been shown to handle crisis quite well.
- Dean Bitterman: Averted. Though on one occasion he threaten Adam to get Henry to stay in the schoolnote or else would send him to Siberia, though later he admit he was bluffing.
- Pint-Sized Powerhouse: He once beat a rhinoceros in a wrestling match.
- The Napoleon: He's a tiny frog that's in charge of the whole school.
- Small Name, Big Ego: And small body.
- Why Did Ithave To Be Snakes: Well,...lawyers actually,
Mrs. Geraldine Sharon Warthog
- Apathetic Teacher: Or secretary in this case.
- Sassy Secretary: Responsible for most of the jokes around Pixiefrog.
- Trademark Favorite Food: Chocolate, which she'll devour upon command.
Mr. Cyrus Hornbill
- Butt Monkey
- Gentle Giant
- Non-Indicative Name: Hornbills are a group of birds found in Asia, but he's actually a rhinoceros.
Mr. Maurice Mandrill
- Hippie Counselor: He's the school's psychologist and music teacher..
Voiced by: Nika FuttermanThe overly-dramatic drama teacher.
- Large Ham: Her voice can go eerily high.
Coach Tiffany Gills
Voiced by: Brian Doyle-MurrayA deep-voiced goldfish and the school's gym teacher.
- Large Ham: She almost always talks in a loud voice.
- Mobile Fishbowl: Teaches from a bowl wheeled around by Vice Coach Horace.
- Vocal Dissonance: You wouldn't expect a goldfish to have such a deep voice, would you?
Vice Coach Horace Ferret
Voiced by: Tom Kenny and Robert Goulet in Animal School MusicalCoach Gills' ferret assistant.
- Cute Mute
- Perpetual Frowner
- Satellite Character: To Coach Gills
- Silent Snarker
- The Voiceless: Except in Animal School Musical
- Weasel Mascot
Mrs. Eugenia Tusk
Voiced by: Cree SummerThe lunchlady.
Nurse Jacquline Gazelle
- Dumb Blonde: She mentioned that she's got a brain the size of a peanut in "Inoculation Day".
- The Medic
- School Nurse
Voiced by: Dee Bradley BakerA whale who is usually seen as the teacher of the nerds. Accompanied by whale noises whenever he talks.