There's a video online of a little kid who looks like he's four or five. And for some reason, the guy filming asks him to list all the SWEAR WORDS he knows. So he does, and almost all of them are PG-13 words that start with "butt" ... like "butt-head" or "butt-face." But then he comes up with one more word you're not expecting.
FCC WARNING: This clip contains the words "butt," "crap," and censored profanity. Play it at your own risk.