Where does this quote come from?

Factual Questions
1

“Meddle not in the affair of dragons, for you are crunchy and taste good with ketchup.”

Ok, not the best or most inspirational quote in the world, but I’ve seen many variations, many atributed authors (From Scott Adams to Anne Mccaffrey to Terry Prachet) but no deffinate origin. Where is it from? Anyone? Anyone? Please, this is driving me insane!

2

“Do not meddle in the affairs of wizards, for they are subtle and quick to anger”. From the Lord of the Rings by J R R Tolkein.

3

Jenericho is right about the true origin, but the version you quote is definitely from Terry Pratchett. (Guards! Guards!, I think.)