The one where Cartman bought "pubes" from that big kid - pretty weird and gross, but hilarious nonetheless. I also like the one where Cartman wants to be a "beefcake" and starts drinking Weight Gain 2000.
Oh, it's got to be Weight Gain 4000 - "BEEFCAKE!!!" Also the "respect my authori-tar" thing. I was a temporary manager at work last summer and i still said that to anyone who would let me.