I found this one on a quiz last night:
"Michelle, ma belle, some say monkeys play piano well, play piano well..."
The real lyrics are in French or something.
The actual lyrics:
"Michelle, ma belle, sont des mots qui vont très bien ensemble, très bien ensemble..."
The words are the French equivalent of "These are words that go together well, my Michelle...", which occurs early in the song.
Another term for misheard lyrics is a "mondegreen", derived from "The Bonny Earl O'Moray", an old Scottish ballad from the 17th century:
"Ye highlands and ye lowlands, oh where hae ye been?
They hae slain the Earl O'Moray, and Lady Mondegreen"
The actual line is "They hae slain the Earl O'Moray, and laid him on the green."
(Laid, as in the past tense of lay, or place)
http://en.wikipedia.org/wiki/Mondegreen