South Park: 10 Worst Things Cartman Has Ever Done

In this episode, Cartman actually managed to do some good: he brought peace to the Middle East and 10 years of Van Halen. He did this by turning a cow ginger (with pale skin and freckles), which is the sign of the end-times for multiple religions. Through reinterpretation, the religions of the world come to peace and party like there's no tomorrow.

Cartman finds no fun in this and threatens to come clean and tell everyone the cow isn't real, while Kyle pleads with him to keep it a secret. Cartman agrees but only if Kyle becomes his servant, insults his mother and feeds him his farts, thus changing his name to fart boy.

Kyle quickly becomes despondent though accepts it as he realizes he has become a martyr to maintain peace, and thus starts acting like a self-righteous douche. And with Kyle's acceptance, the farts come even more thick and fast, until Stan, worried about his friend, lies that the cow was a miracle, breaking the peace as that wasn't the prophecy.

Sucking farts was bad enough, but Kyle realizing it was all for nothing made it one of Cartman's worst crimes.