Mondegreen

A new word in the updated Merriam Webster's Collegiate Dictionary, Mondegreen is a fun word to know about. 

Mares eat oats and does eat oats and little lambs eat ivy. A kid'll eat ivy, too. Wouldn't you?
...[From] part of a popular nonsense song of 1943 called "Mairzy Doats"--per ASCAP Hit Tunes booklet, written by Milton Drake, Al Hoffman,and Jerry Livingston. The beginning is more or less rendered:
Mairzy doats and doazy doats, and little lamzi tivy. A kiddely tivy too, Wood'n you?

Is a prime example, though nonsense. The term Mondegreen comes from Percy's Reliques:

Ye Highlands and ye Lowlands,
Oh, where hae ye been?
They hae slain the Earl Amurray, [sic]
And Lady Mondegreen.

Where the final line is actually "And laid him on the green."

I always thought a line from an old tune was "Just for your coveted sequence." when it is actually "Just for you, covered in sequins."

Don