Hmm, man tough choice there dude!
1. Hippy episode most likely, I love that episode. That or the one where Cartmen blows a funny fuse.
2. Probably the part with Wal-mart when Wal-mart dies and craps itself. Or when the Wal-mart guy goes "Now I will reveal my true form!" and rips off his mustache.
3. "Everyone knows hippies can't stand death metal!"