10. Ozzy Osbourne
This one was pretty brief, but it was glorious, nonetheless.
In the season 2 episode, "Chef Aid", everyone's favorite elementary school chef finds himself at the receiving end of a lawsuit from the tyrannical Capitalist Records. After discovering that Alanis Morissette plagiarized his song, "Stinky Britches", he seeks to have himself credited. Instead, the record company not only refuses, but hires Johnnie Cochran to sue Chef for harassment. If he can't come up with his legal fees in 24 hours, he'll be forced to spend four years in prison.
Chef prostitutes himself, while the boys try to help raise funds. Part of the boys' grand plan is to put on a benefit concert for their dear friend, inviting a multitude of musicians, all of whom Chef helped in some pivotal way.
Among them is the Prince of Darkness himself: Ozzy Osbourne. He explains that when he was just starting out, Chef told him to buy a pompadour hat. He thought Chef said, "Bite the head off a bat", solidifying his hardcore image. He goes on to bite Kenny's head off just moments later.
Sure, it only lasted a few seconds, but also, think about this: Ozzy Osbourne killed Kenny. Come on, now.