Eric Cartman
Trey Parker and Matt Stone explained on the DVD commentary for "Towelie" that the character was conceived as a joking reference to the over-marketing of characters in the wake of the series' success. Eric Cartman, partially breaking the fourth wall, delivers the penultimate line of Towelie's eponymous episode: "You're the worst character ever, Towelie", to which Towelie responds, "I know."