I have only been watching SP for the past year or so, so I'm sure there's a lot of episodes I haven't seen, and I'm obviously a little late getting on the bandwagon. But a couple of weekends ago they did a "25 most outrageous episodes" thing, and one of the episodes was where Cartman had this J-Lo hand puppet where he recorded songs and did some *ahem* other things involving Ben Affleck. I don't remember laughing at anything so hard in my life.
Oh, and of course the episode with Mr. Hankey and his drunken, verbally abusive wife.
So what's your fave?