What a complete waste of time. Tenacious D is the most bottom rack, low brow, under achieving comedy I have seen in a long time. I often find Jack Black really funny. In Jesus' Son, he was awesome ("we must stop and get it, we can feed off it's haunches!"), in King Kong he was mildly dramatic, in Nacho Libre he was passable. In The Pick of Destiny, come on, this is just, as he would say in the movie "f*cking lame man!"
This feels like your average crappy kids movie ala Beethoven's 2nd or whatever ______. The story even follows the same sort of character building and plot. Find the thing, change their lives, thing breaks, realize they don't need said thing. The only difference is to apply liberal swearing to it. Without the swearing, this movie would probably get a G rating without it.
Terrible and I feel stupider for watching it all the way through.