| Description | Character |
| Protagonist and title character | |
| Blue-skinned best friend | |
| Blonde, athletic love-interest | |
| Anthropomorphic dog, lives in an igloo | |
| Purple-skinned rich girl, daughter of Bill Bluff | |
| Oddball older sister | |
| Father, creator of 'The Ol' Funnie Fireball' | |
| Mother, usually meek-mannered and somewhat ditzy | |
| Male neighbor, has many 'very expensive' inventions | |
| Female neighbor, known for sarcasm and deadpan comedy | |
| Super-jock, friend of almost every student at Bluffington School | |
| Sweet, naive, heavy-set girl | |
| Local ice cream and candy salesman | |
| Green-skinned antagonist | |
| Spoiled, antagonistic, female cat (thought to be male, but eventually had kittens) | |
| Paternal grandmother, stereotypical grandmother type | |
| Maternal grandmother, owns a motorcycle and loves to disco | |
| | Description | Character |
| Intelligent green-skinned twin brothers, geeks | |
| Often mentioned, but never seen troublemaker | |
| Member of the antagonistic gang, former mayor's son | |
| Assistant principal, strict and stern disciplinarian | |
| Green-skinned, grandmotherly elementary school teacher | |
| Richest Man in town, descendant of Bluffington's founder | |
| Wife of richest man in town, owns and teaches at a ballet studio | |
| Former mayor of Bluffington who becomes the middle school principal | |
| Member of the antagonistic gang, only member who is nice to the main character | |
| Foul-tempered coach, sexist and unconcerned with the well-being of his students | |
| Overly-childish guidance counsellor, wears 'Hug Me' sweaters | |
| Band, known for hits such as 'Killer Tofu' | |
| Member of the antagonist gang, most intelligent of the gang | |
| Nephew of assistant principal, tall, mean, incredibly stupid and tough | |
| Dark green-skinned foreign exchange student from Yakistonia | |
| Light-green skinned girl who takes an interest in Skeeter | |
| Never-seen elementary school principal, much kinder than his assistant counterpart | |
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