March, 22nd, the year Cartman turns four: this is the date of the day Cartman first sees Kenny. He's in the process of throwing a temper tantrum because his mother bought him a bunch of expensive new toys, and has included his broken old toys (Cartman has a tendency to break the things in his possession) in her yard sale. Mr. McCormick pulls up in his pickup because it is Kenny's birthday, and he is looking for a present. Cartman pauses in his fit because his mother's attention is diverted, and he locks eyes with Kenny (the only visible part of Kenny), who is strapped into the passenger seat in a car seat—a very unsafe place for a four year old, but Mr. McCormick has learned it scarcely matters.
This is before Cartman has any concept of money, of rich and poor. At three he assumes that people with nicer stuff simply choose to have nicer stuff, and the only reason someone would buy broken toys at a yard sale for a fourth birthday gift is because they're stupid.
This is the reason Cartman becomes Kenny's friend: he wants access to the toys his mother sold Kenny's father, the toys he still considers to be his.
o o o
Cartman is five when he learns what death is from an old Sesame Street rerun. Death is when people don't come back, ever, and Cartman realizes that whatever Kenny has been doing all this time, it isn't dying. Cartman wastes no sentiment on him from thereon out and adopts a certain smugness when he thinks of how much more informed he is than Stan and Kyle—a sense of superiority that festers and grows into sociopathy by the time Cartman enters fourth grade.
o o o
"It's—fucking—freezing," Kenny forces out, teeth chattering, hands in armpits, parka drawstrings pulled as tightly as possible as he follows Cartman up the South Park volcano, stepping in his companion's footsteps so that he doesn't have to trudge through the waist-deep snow.
"Quit your bitching; it isn't that cold," Cartman says. Cartman, who is wearing a brand new down jacket, while Kenny wears a parka that gets thinner every year.
"This is the temperature penguins freeze at," Kenny grumbles, but follows nonetheless.
Cartman is ten and Cartman has a hypothesis. If monsters exist, he reasons, than Kenny must be some breed of them.
He leads Kenny through the wilderness, up to a crag, and casually surveys the town with his hands in the jacket pockets, whistling a Mother Goose-ian tune in a perfect imitation of innocence. Kenny hops from his left foot to the right, shivering and scowling. "What was so important you had to drag me up here, Cartman?" he demands, and Cartman motions toward the mountain edge. Kenny ventures forward and squints, expecting something spectacular.
He never sees Cartman's hands shoot out behind him, landing square on his back and shoving—Kenny falls thirty feet and lands with a gentle flump in the snow, and Cartman scrambles down gleefully to investigate his remains.
In the end Cartman is disappointed. Kenny doesn't twitch and moan for brains like a zombie, or turn into a bat and fly away—he doesn't do anything but lie there, in fact. "Like all poor people," Cartman grumbles, and toes Kenny's bloody shin.
That is the year Cartman outgrows monsters; he stops using his night light and scoffs at ghost stories and the movies that give his friends unsettling late-night dreams.
o o o
Cartman is sixteen when he first becomes curious as to what Kenny is. He knows he isn't anything supernatural—hypothesis tested and disproved—but he knows he isn't human, either. Humans die, Kenny does not die, ergo Kenny can't be human.
Kenny has a job at the carnival, manning one of the stomach-churning rides. He spends that summer pushing buttons and standing in the sun. Cartman spends that summer watching Kenny, glaring thoughtfully at his sunburned neck and hand-me-downs.
"Hey babe, free mustache ride!" he calls to the occasional passing girl, and Cartman snorts and says "You haven't got a mustache, dumbfuck." Kenny shrugs, and his eyes linger on the armful of confections and carnival delicacies Cartman always has on him; there are few things Cartman likes better than eating in front of hungry people, and he feels Kenny deserves it for being such an irritating conundrum.
o o o
Cartman inherits a motorcycle when he is twenty and his uncle dies in a bad highway accident. Cartman complains loudly about all the repairs that have to be done before the bike will be in driving condition; he complains to Kenny while Kenny works on it, and gives him a running commentary on the motorized world.
"And why should the handicapped get all the good parking spaces? They're a drain on society. They should all be euthanized. With hammers."
"You're a fucking horrible person," Kenny grunts, pushing his bangs out of his face and leaving streaks of grease in his hair. "I don't know why I hang out with you."
Cartman does. At age twenty, everyone who is going to leave South Park, has left. Cartman and Kenny, neither of whom have the means to get out, have been left behind.
o o o
Riding a motorcycle around a small town gets old, fast. It is not long before Cartman has exhausted every creative option, including riding through the playground on a Saturday morning. Cartman knows it's bad when the sound of children screaming doesn't cheer him up.
Cartman plans his 21st birthday road trip without consulting either Kenny or a map. He just guns his engine outside Kenny's window until Kenny comes down, and then he tells him he's going to Vegas with him to help him cheat at blackjack—"Because all poor people are born with the ability to count cards."
"Cartman, you don't even know how to get to Las Vegas."
"Kenny, everyone knows that all roads lead to Vegas."
"That's Rome, dickhole."
"There aren't any roads over the ocean, dumbass."
Predictably, they get lost. They stop at a rest stop and Cartman bullies Kenny into a game of I Spy; he makes Kenny guess which of the dozens of cows is the "something black and white" for twenty minutes before he taps his black and white coffee cup.
o o o
Cartman refuses to go home without getting completely shitfaced, because it is his 21st birthday and this is America. He and Kenny purchase substantial quantities of alcohol and a hotel room and start drinking. Kenny gets drunk enough to confess that Cartman was the first friend he had and now he's the last friend he has and maybe that's why..., and then he gets drunker. Drunk enough to kiss Cartman, then drunk enough to fumble for his zipper and give him a shoddy blow job.
Cartman rolls over when he's done and Kenny stares at his back, breathing unevenly, mouth wet, and it sinks in that Cartman, in true Cartman-fashion, got what he wanted and wasn't about to give anything back. "You're a fucking horrible person. I don't know why..." Kenny goes into the bathroom and Cartman can hear him jerking off.
After years of wondering, Cartman has finally decided what Kenny is: a malfunctioning machine. Cartman has long held the belief that all other people are automatons and that he alone is a thinking, feeling being. Cartman looks at the sparse black people in South Park and sees out of date farm equipment; the numerous local prostitutes around town are like the old 25¢ kiddie rides in front of grocery stores. There must be a glitch in Kenny's program, Cartman reasons, because that is the only way someone would love a person like him.