I ran across this story about a California company's quest to bioengineer real mythical creatures. It sounds like something out of a Michael Crichton book.
"Here be dragons: With luck, you may soon be able to buy a mythological pet"
Near the end is a link to another story about a previous idea the founder of the company had, which involved engineering fish with real gold in their scales. I guess the weight of the gold made it impossible for them to keep afloat.