Hibbert: You know, isn't it interesting how the left -- or sinister --
twin is invariably the evil one. I had this theory that... Wait
a minute. Hugo's scar is on the wrong side. He couldn't have
been the evil left twin. That means the evil twin is, and
always has been... Bart!
Bart: Oh, don't look so shocked.
Hibbert: Well, chalk this one up to carelessness on my part.
-- Pobody's Nerfect, "Treehouse of Horror VII"