He also does the voice for the player character in Brutal Legend, and he’s done at least one real short crossover between Brutal Legend and Metalocalypse. (Speaking of which, the second Dethklok album is out. Still waiting on William Murderface’s solo project....)
I was kind of surprised Brutal Legend (which is doubtless what he’s promoting) didn’t get an official tie-in with The D. It’s totally the same mentality and humor, the fantasy world of heavy metal where all the satanism is real but in a funny way.