Original Children's Song Lyrics

Brunetter’s thread about “The Wheels on the Bus” song
( http://boards.straightdope.com/sdmb/showthread.php?threadid=57609 ) got me wondering:

What children’s songs have you changed the lyrics to? I’m talking about adding things to a song. For example: I’ll sing “The Wheels on the Bus” song, but after the usual verses, I’ll add a few others like, "The hookers on the bus say ‘Hey there, babe.’, and in “Old McDonald”, we have Elvis Impersonators "with a ‘Hunka Hunka’ here and a ‘Hunka Hunka’ there.

So what lyrics have you replaced in popular children’s songs?

I have one, but I expect it’s highly inappropriate…