And the joke is
when he awoke his
body was covered in goat piss

The story:

Unfortunately, its not that embarrassing. While singing along with the song in the car we had a debate about what the lyrics actually were. I had everyone convinced I was right, and if you listen to the song you can hear them say "goat piss" but once it was checked on the internet it turned out to be coke fizz, but we still all sing "goat piss" because, dammit, it's funnier.