Rebecca and her brother lived in a very sheltered, home-schooled life with their parents and with very little exposure to the outside world. They were both seen as intelligent but lacking in social skills, and until the spelling bee had not seen the outside town or interacted with other children their age. While Mark wanted to go to a public school after meeting the other children, Rebecca had no interest in the outside world and chose to stay at home. She was noticeably twitchy and anxious. Rebecca wears a lime green coat with a deep magenta collar and a long yellow skirt. Her hair is rather curly and is held back at each side by two round, red barrettes parting her bangs. Though she is intelligent and studious as well, Rebecca is naive and sheltered from the ways of the world and rather introverted. Her awkward behavior and reclusive personality stem from her lack of social life. Despite this, she’s in a relationship with Kyle and is very clingy to him, which he doesn’t mind. Rebecca is English.

Mark wears a deep green pullover sweater, with a white dress shirt and a black tie underneath, and black slacks. His hair is dark brown and slightly wavy, with a parting in the bangs. He appears to be the older of the two siblings and is the more outgoing one, curious about what life was like outside their home and eager to explore the public school, wanting to see what other boys were like. Though he is incredibly intelligent, he was also naive in a few ways; seeming astonished that "friends" would call each other names and fight. Mark convinced his father to let him attend public school, and he does not understand Stan Kyle Cartman and Kenny’s relationship dynamic. Mark is English.

Cartman is a 9 year old boy. He wears a bright-red winter coat and bright-yellow winter gloves. He wears a teal-blue winter cap hat with a flat yellow puff on top, brown khaki pants, and black shoes. Cartman's hat also has a yellow matching trim on it that matches its puff ball and gloves.. He has medium-brown hair. Cartman is described in various terms, in short, he is a funny, vicious, angry, good (sometimes), bad, nice (sometimes), self-absorbed, immature, destructive, sarcastic, snooty, loud-mouthed, lazy, and hilarious fatass. He is the most foul-mouthed character in the show. He is also a racist bully and stereotypes almost everyone he sees. The very dark, usually disturbing undertones to his personality often hint at an extreme mental imbalance. Apart from being portrayed as having a general lack of moral responsibility or social conscience, he also seems to take pleasure from others' misfortune and is generally unable to show empathy, although there have been exceptions.

Stan Marsh is a 9 year old boy. He has blue eyes and a medium-light skin tone. He has short, black hair. He is mostly shown wearing a brown coat with a red collar, a royal-blue winter cap with a red pom-pom ball on top of it and matching rim on the edging of the cap, and dark-blue jeans. Under his coat, he either wears a red and blue baseball shirt or a white t-shirt/V-neck. He also wears a blue Terrance and Phillip shirt to bed and a green suit for special occasions. Stan is generally the most tender and sensitive of the four boys. Stan is also shown to be a pacifist, as he is often the one who breaks up fights between his friends, especially Kyle and Cartman, and he prefers to find peaceful solutions to problems. He is usually the one who is unaffected by the many scams, cults, and mass influences that South Park has been subjected to, and has a knack for seeing through falsely glorified practices and celebrities.

Kenny is a 9 year old boy. Kenny has messy blond hair, blue eyes, and a pale skin tone. For his outfit, he wears an orange parka, orange pants, and black shoes. On occasion, usually when he is scared or crying, he will pull the strings on his hood to make it tighten, although he did this once after Cartman had farted in an unventilated space on an airplane. Kenny is the second kindest, sweetest, and most sensitive and tender member of The Boys after Stan. He is also the smartest of the four main boys after Kyle. He is also the most sexually knowledgeable and most sexually experienced of the group. In earlier episodes, when an unknown term is introduced to Stan, Kyle, and Cartman, Kenny will be called upon by his friends to clarify, although Kenny sometimes does not know the meaning of the term himself. His muffled responses are often met with laughter.