The 'shroom'/sasquatch scene is pretty funny!
I've never actually gotten high, but I have to believe that this movie would be effing hilarious to watch after smoking up. It's pretty funny anyway, because Jack Black is funny as hell. But probably if you're stoned, it's even more hilarious, I'm sure.
I never listened to Tenacious D music before seeing the movie for the first time about a month or 2 ago, but I actually really like their stuff. History is a great tune and I really like it a lot. I hope to see them in concert sometime. Are they still touring?