The first time Cartman comes into his own hand is the day he truly becomes a man. He's thinking about Kyle sucking his balls when it happens, one of his earliest and tamest fantasies. He can hear Leane enjoying her "gentleman company," through the paper thin walls. He pictures it without meaning to and shoots off like chinese gunpowder.
Spent, he exits 4chan, clears his browser history, and takes a cold shower. He entertains the thought of murdering the man in the other room, but settles for slashing his tires tomorrow if he still feels up for it after breakfast.