Actually I lied. There's only one rock opera about milk, and it's this one. And I think you'll agree that it is the only rock opera about milk that is actually needed.
Battle for Milquarious.
Edit: Okay, I don't know how to stop that from starting at 17 minutes in. It makes it even more confusing. Please to be manually moving the cursor to zero...
Sadly for Milquarious, it is actually an ad for the California Milk Processor Board, made by ad agency Goodby Silverstein & Partners of San Francisco, but I did hear Electric Six was involved somewhere.