Evil Stewie

Evil Stewie was the clone of Stewie Griffin in Family Guy. He only appears in the episode The Hand That Rocks the Wheelchair.

History
Evil Stewie looks almost exactly like Stewie. However, Stewie wears a yellow shirt and red overalls, whereas Evil Stewie wears the opposite: a red shirt and yellow overalls. When Brian told Stewie that he was going soft when he failed to shoot a boy, Stewie invents a machine that is supposed to make him more evil, but instead creates a clone of his evil self.

Later, Evil Stewie stuffs two batteries up Brian's nostrils and strangles him with his collar. Stewie comes along and Brian fears him, thinking he was the one who tried to kill him. Brian then sees the evil clone behind Stewie, and Stewie decides to do some testing on him. However, the Evil Stewie brutally beats him up. He then cuts off Brian's tail with a pocketknife, and tries to choke Stewie with it. He then slices a woman in half, and steals her car. He lures the Kool Aid Man to his demise and then beats him with a baseball bat. At the end of the episode, Brian is tied to a pole, luring in Evil Stewie to kill him, just in time for Stewie to catch him. The two engage in combat, with both their clothes are removed, leading Brian to choose which one of them to shoot. Brian comes up with a simple solution, and Evil Stewie is killed. However, as Brian and Stewie were leaving the park, Stewie turns around with yellow cat eyes, and a nightmarish laughter is heard. If Brian didn't mistakingly kill the original Stewie, it is also possible that Stewie may have regained some of the evil that he lost from early episodes.

Evil Stewie's creation, plus the plot of the episode, was likely made as a gag to how Stewie's behaviour changed through the show. In early episodes, Stewie seemed downright evil as he constantly planned to kill Lois (among other acts), in contrast to later episodes.