Leopold "Butters" Scotch is one of the other fourth grade students on South Park and got his day in the sun when Kenny was permamanelty killed during the sixth season. Butters replaced Kenny temporarily, but was soon replaced with Tweet Tweet. Now Butters is still sucked into the group's antics and is often manipulated by Cartman to join in on his evil plans.
Sometimes Butters has been known to dress up as Professor Chaos when he can't handle any more abuse to exact his revenge.
Cartman: So weak, dude. Dark times, brah. Dark times.