Tenacious D is a two-piece musical act, and this HBO series documents their many struggles as friends, and as a band of two very absurd individuals.
The looks of Jack Black and Kyle Gass are part of the comedy. They are unlikely rock stars, and after the series, they have begun to tout themselves as the greatest rock act ever. Their looks totally contradict their rock attitude and that is where most of the humor comes from. They are hilarious and Black's delivery makes the show.
Jack Black: Kyle. Did you look underneath THE BAR?
Paul: Ok, you guys, seriously, sincerely, you have to get out of here. We're closed.