My late friend Paul Keene had 2 excellent parodies. The first a parody of one of the best known Johnny Cash songs, I walk the line. as follows:-

I keep a close watch on this love of mine,
I keep my pants tied with a piece of twine.
Baby, if you say you'll be mine,
Come round some time, I'll cut the twine.

The other to be sung when there were either too many "finger in left lug-ole" merchants or those that were there were taking the music too seriously was a wonderful piss-take on the Voyage of the Calabar.