Seeing Chris and Cosmo get tortured by the Metal people (what ever their names are, I haven't been watching season three.)all of Sonic's suppressed anger releases and he becomes Dark Sonic. Strangely Eggman (robutnick)is the one that snaps him back to his senses and Shadow gets to be the hero. (yay)

http://www.youtube.com/watch?v=XtvplkXKSaY