mc5 - I'm not wearing any pants!

Take a familiar (or at least famous) quote (e.g. "Don't go around saying the world owes you a living. The world owes you nothing. It was here first." by Mark Twain). Then find a good stopping point (e.g. "Don't go around saying"). After this, add the phrase, "I'm not wearing any pants (e.g. ""Don't go around saying, "I'm not wearing any pants!").

Stevie

Weeeeeeeeeee
wish you a merry Christmas
We wish you a merry Christmas
We wish you a merry Christmas
Not wearing our pants.

Stevie

And my absolute favorite bop-along carol (bass part in italics):

Joy to the world! the Lord is come;
Let earth receive her King;
Let every heart prepare him room,
Not wearing any pants
Not wearing any
Not wearing any pants
paaaaaaants, Not wearing any
Not wearing, not wear-air-airing any pants
paaaaaaants, not wear-air-airing pants, pants, pants

Falstaff

"Yes, I agree, there does appear to be a draft in here. I'll go and put on my pants!!!"