Kyle is a smart, caring, and principled fourth grader who frequently serves as the moral center and voice of reason in the friend group, though he is equally known for his sharp tongue and quick temper. Kyle is one of the smartest kids in his class and a straight-A student. He excels in computer technology, video games, music, and academics. He often uses logic to analyze complex situations before the other boys do. Despite his good intentions, Kyle has a short fuse and is prone to intense outbursts of anger. When pushed too far—especially by Cartman—he loses his patience and yells or fights back physically. Kyle shares an intense, volatile rivalry with Cartman. Cartman frequently targets Kyle's Jewish faith (and the fact Kyle is a Jew himself) with antisemitic insults, which triggers Kyle's fierce defensiveness

Cartman lacks a moral compass and derives direct pleasure from the pain, humiliation, and suffering of others. He possesses an inflated sense of superiority, refusing to accept personal flaws (such as denying he is overweight). Cartman is manipulative, narcissistic, and sociopathic driven by instant gratification and a lack of empathy. He views himself as superior and demands constant attention or special treatment. He actively derives pleasure from the pain, humiliation, and misery of others, especially targeting Butters or Kyle. When crossed or angered, he reacts aggressively without long-term calculation of the consequences

Kenny is a loyal, deeply empathetic, and surprisingly protective friend who balances a crude sense of humor with heroic, self-sacrificing core. Kenny cares deeply about his friends and is frequently willing to lay down his life for them or strangers. he possesses an advanced, often explicit knowledge of adult topics and sexual concepts, which he speaks through his muffled orange parka. Having grown up in severe poverty with dysfunctional parents, Kenny has a tough, go-with-the-flow attitude. He loves his younger sister, Karen, unconditionally and goes to great lengths to protect and comfort her from their harsh reality at home.

Craig is cynical, stoic, and deadpan pragmatist who is famous for his monotone voice and compulsive habit of flipping people off. Craig is unimpressed by the chaotic events happening around him. He rarely gets excited or emotional, preferring quiet and boring situations. Unlike the main group of boys or Cartman's grandiose schemes, Craig relies on simple, realistic, and logical solutions. He often points out when a plan is pointless or doomed to fail. He leads his own clique known as Craig's Gang (which usually includes Clyde, Tolkien, and Tweek), serving as a recurring rival and foil to Cartman's group.

Butter is sweet, incredibly gullible, and chronically optimistic, serving as a wholesome contrast to the others. Butters is sheltered, polite, rarely swears, and often misses the cynical or vulgar jokes his peers understand He faces constant misery with a cheerful attitude and finds joy in simple things like ladybugs or tap dancing. He is deeply terrified of his strict parents and panics at the mere thought of being grounded.

Tweek is a chronically anxious, hyperactive, and paranoid. Tweek is constantly jittery, twitching, and prone to explosive panic over minimal pressure. He frequently defaults to worst-case scenarios and fears abstract threats like global events or aliens. His frantic behavior is driven by an intense addiction to coffee from his parents' shop, Tweek Bros. Coffee. His parents mistakenly attribute his meth-fueled jitters to ADD rather than caffeine

Clyde is best known as a sensitive, impressionable crybaby who is easily swayed by peer pressure and obsessed with popularity and girls. He struggles significantly in school, famously answering basic math equations incorrectly and demonstrating overall low intellectual capability. Unlike the more cynical or complex main boys, Clyde is heavily focused on typical childhood trends, crushes, popularity, and girls (such as his brief relationship with Bebe Stevens). He can be easily conceited when praised—such as when he was voted the "cutest boy" in class—yet he remains deeply insecure and easily manipulated by his peers.

Tolkien is calm, rational, and level-headed personality, often acting as the grounded "straight man" to the chaotic behavior of the other kids. He is generally level-headed, cool, and slow to anger, even when dealing with Cartman's constant microaggressions and racial stereotyping. He speaks in a dignified, articulate manner and is portrayed as one of the smarter, more mature. He frequently stands up for his rights and handles being singled out or tokenized with quiet dignity, though he occasionally expresses frustration at being treated differently because of his race or wealth.