Horribly Animated, crude, juvenile humour, toilet humour, potshots at various celebrities (Notably as an apparent curse word, Barbara Streisand) and horrid language...

But I never laughed so much.. It was actually quite good.. Much better than most episodes of the show (Except the one done in Spooky Vision.. movie about equals that one)  

All in all, a very good movie, but DEFINITELY deserves the rating...  If nothing more, just for the chorus of that one song..
"Shut your fucking face, unclefucker"