EARTH: Bart's twin, Hugo

An alternate version of Earth: Simpsons where Bart has a conjoined twin named Hugo who was separated at birth and hidden in the attic under the assumption that he was the evil twin. Hugo escapes and plans to reattach himself to Bart, only for it to be revealed at the end that Bart was actually the evil twin all along. Hugo joins the family while Bart takes his place in the attic.