A South Park editor revealed what Kenny says in the beginning in every South Park intro (which, like most of his dialogue, is muffled by his parka).
For the first 2 seasons he really says, "I like girls with deep vaginas, I like girls with big fat titties."
From season 3 and beyond, it was changed to "I have got a ten inch penis, use your mouth if you want to clean it."
For some of the later seasons, it was changed to "Someday I'll be old enough to stick my dick in Britney's butt," referring to Britney Spears.
It Is Unknown what the Current Lines are.