The gym teacher, and the only staff member who can teach; he can be seen as the protagonist for these reasons. He refers to himself as "Larry L." because he is embarrassed by his last name, and his catchphrase is "Why can't someone else teach P.E.?". He is apparently the only qualified teacher, but he lost the science-teacher position to Miracle Grohe because of her "nude" presentation (which, for censorship reasons, was never shown). He is hopelessly in love with Miracle, but at the same time can't stand how airheaded she is, so he insults her instead of telling her how he feels. He has been shown dating other women, but still goes into dazed states when around Miracle. In an early promo for the series, the character was named Larry Slimp.
- Innocently Insensitive: He tends to insult Miracle without realizing it at times (though other times he's just fed up with her stupidity)
- Like Father, Like Son: His dad also has a comfort kitty of his own and while works for the army, doesn't do any fighting.
- "Well Done, Son!" Guy: Feels badly about not being in the military like his father.
A spiritual, hippie-ish, perpetually barefoot science teacher who often brings her infant son Merch (who has been shown to be smarter than his mother) to school as she believes that babies should always be with their mothers. Though she is a science teacher, she believes in things a science teacher wouldn't (Mother Earth, mysticism, fortunes, etc.). She is also very gullible, for example taking the compliment "you're too pretty to be in school" as a statement. It is implied throughout the show that she also likes Larry, but gets angered whenever he doubts her spirituality. Her mother, seen in a flashback, had her as a teenager. She also runs an underground Pillow Fight Club (a parody of Fight Club) that appears to be worldwide.
- Non-Standard Character Design: The only one to have colored irises.
Assistant Principal. His catchphrase is "I need a catchphrase!" Usually smiling and relatively jubilant, he is the most oblivious character in the show, clearly shown when he stated "He is so oblivious he probably doesn't even realize he is talking about himself" when he was talking about himself. Before becoming assistant principal he worked as a prison clown in a Florida penitentiary, and in "Miracle's Are Real," performed a disturbing song for Larry while dressed up as a clown in a black-and-white-striped prison jumpsuit. Stuart has a habit of shortening the word "assistant" to simply "ass" (such as "ass principal" or "ass coach") on job titles. He has a sister named Polly, whom he enjoys imitating and even dressing as; he pretends to be her to go on a date with Larry. He seems to be particularly interest in Larry, but as the series progresses, he develops a soft spot for Sue, spending the episode "Hurricane Willard" trying to impress her, performing a puppet show and gifting her with a wireless microphone. It is heavily suggested throughout the series he is completely insane.
- Ambiguously Bi: He's been hinted at being interested in Larry, Sue and Andrew.
The "acting" principal of Knob Haven. She got the job due to a mysterious accident involving the last principal and a pair of metal claws. Sues style is stern, firm and to the point. In her eyes, there are no dumb questions, just plenty of dumb people. As evidenced by her last name, she rarely (if ever) says "Yes." Her catchphrase is "No." She is also a hypocrite, clearly shown when she stated that she would have quit before firing any of the teachers, just to moments later fire Willard, and again when she pressured everyone to keep the School Fair fair, she cheated during the raffle. She is also shown to be incredibly lazy, giving the bare minimum to Miracle so she could become a teacher again because she didn't want to do the work of finding a new teacher, as well as saving the teachers who suffered a heart attack because she didn't want to have to do the paperwork. This as well as having no care for her fellow staff, as when she saw them have heart attacks, she just gave herself the rest of the day off, as well as planning to blame all of the school's problems on them at a meeting in Washington D.C. It is revealed in the episode "Hurricane Willard", her full name is Susanna Louise Sezno. She is rarely in the spotlight when it comes to love interests, hooking up with Happy in "Back In Time" and becoming impressed with Stuart at the end of "Hurricane Willard."
- Crossdressing Voices: Voiced by Kenan Thompson.
- Not So Above It All: Has her moments of selfishness and corruption.
- Suspiciously Specific Denial: There is NOTHING going on in the auto shop garage.
The secretive custodian. In the first few episodes, he speaks only in Arabic, which is overdubbed by an English translation that also makes comments about Happy as well, similar to a narrator. In later episodes he speaks fractured English and no longer has a translator. He lives in a shack on the school grounds. His catchphrase is roughly translated into English as "I am fond of America", though the way he says it sounds like hatred toward America. The actual words are a mondegreen for "I am fond of America", so it might be a mistranslation on his translator's part.
- Overly Long Name: His real name.
The flamboyant and bisexual drama teacher. His catchphrase is "Speak up." In Spanish, Andrew's last name roughly translates to "he likes both", a reference to his bisexuality. He is in love with both Miracle and Larry (though he did develop romantic feelings for Stuart after seeing his breasts), hoping they get together so he could get together with them, though it's rarely shown in future episodes. He later becomes a narcissist after seeing himself in a dress. He resents Jose Canseco, for an incident that happened in his childhood when he played baseball as a child.
- Meaningful Name: His surname is Spanish for "he likes both."
The unappreciated librarian who often gets mistaken for objects such as brooms or toilet brushes, leading her to become angry when people ignore or cut her off. Her catchphrase is "Quiet down!". She seems to have high levels of testosterone, which is balanced out by taking female hormone drugs (which Vice Principal Prozackian was given when it was believed that the hormone drugs were steroids). Helen is skinny but is considered unattractive in relation to Miracle. In one episode, it was revealed because of her extreme loneliness, she has a habit of falling in love with inanimate objects and lives with a lot of cats. She has a close friendship with Andrew, as the two frequently talk and exchange gossip together. She was an alumnus of Knob Haven High School, where she and Sue formed a musical duo, and she was obese back then.
- Cargo Ship: Tends to date/fall in love with inanimate objects.
A middle-aged German teacher with very low self-esteem. His catchphrase is, "If I believed in reincarnation, I'd kill myself tonight." He still is highly influenced by his mother for whom he used his position as a driving teacher to run errands. In one episode, he promised to dump his girlfriend because his mom said "she was a whore." In another episode, when presented with the option of a beautiful woman wanting to marry him, he responded, "I'm sorry. I promised my mother I would die alone." He's constantly fretting about his job and is normally homeless to the point where he lives in completely random places (the school football field, in the belfry of a tower, in the closet in the teacher's lounge). He has a fear of driving that stems from crashing his car into a drive-in theater screen during a sexual experience. To get around, he arranges for emergency vehicles and hearses to pick him up and take him where he wants to go by lying about sickness, fire, or death. Later, after he obtains the position of the school's driving instructor, he begins using the driver training car for his personal transportation. He also doesn't have an e-mail account or a phone. He has a habit of being a blabbermouth. In the 1930s, became infamous for making love with his teacher, and was known as "The Whoop-De-Doo Kid." He also apparently forages the school dumpster for food every day at 3:00. Despite his feelings of isolation due to his mother and terrible social skills, Ennis sees Willard as his closest friend and constantly takes it upon himself to defend him from any perceived taunting. In the episode "Tackin'" it is revealed by Ennis his middle name is either Leonard or Herbert.
- Extreme Doormat: He's prone to being a suck-up with all the teachers, to the point of sucking up to HITLER of all people.