Mark Cotswolds is a home-schooled kid that took part in, and won, the 15th Annual South Park Spelling Bee in "Hooked on Monkey Fonics".
Mark was very sheltered in their home-school life and, until the spelling bee hadn't seen the outside town. Mark wanted to go to a public school and begged his father for the chance.
Mark, who had been made to go to school in a giant hamster ball, experienced bullying at the hands of the other boys and wound up duct-taped to a bench. Though his father wanted him to return to homeschooling, Mark convinced his father to let him go continue public school, and go to the school dance.
At the school dance, Mark confronted Kyle Broflovski for turning Rebecca into a slut, and proceeded to beat him up. The other boys became impressed, now wanting to hang out with him and include him in their circles.
Though their father tried to intervene and take them out of the dance, Mark convinced his father to let them go to public school, as the two of them would still have to face bad things someday, and it would be better to face them now.
Since the episode, Mark has reappeared in the show, making cameos in "Professor Chaos", as a potential fourth friend, "The Death Camp of Tolerance", in the group of kids sent to the camp (when they first appear) and "Imaginationland", at Cartman's party.
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 of 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, that the boys seemed to "like, yet hate" Pip at the same time, and how the other boys laughed at Kyle for liking Rebecca. Though he was continuously bullied by the others and found himself duct-taped to a bench, he was unconcerned and grew more curious each time.
Despite his parents' objections, he remained eager to explore the outside world and ultimately gave a speech explaining why it was all right for him to stay in public school.
He seems quite protective of his sister, beating Kyle up after seeing what he had inadvertently turned her into, which the other boys then considered him to be "badass" for it.
By the end of his debut, he was finding his way into fitting in with the other boys, calling Stan a "gaywad" in response to being called "nerdo".
- "Hooked on Monkey Fonics" - Mark and Rebecca win the spelling bee. Mark is intrigued by other kids and wants to join public school.
- "Professor Chaos" - Mark is one of the contenders to replace Butters, but doesn't make the cut past the first elimination round.
- "The Death Camp of Tolerance" - Mark is seen at the camp when the boys first arrive.
- "Raisins" - Seen in Raisins from the back.
- "Smug Alert!" - Mark is seen at party.
- "Imaginationland" - Mark appears at Cartman's party.