I believe in the "Held Back" episode, whilst watching a video,, Butt-head asks Beavis if he hears dark voices. Beavis' response (approximately):
"No but I hear some white guys, a Chinese dude, and a couple of Mexicans."
Butt-heads continues to ask what does the "Chinese guy say",
Beavis, in high voice, " Pull down your pants, spank your monkey."
Butt-head, "Whoa, what did the white guy say?"
Beavis, "He says the same thing, but he sounds like me."
Dennis