Bill Cipher is the main antagonist of Disney's Gravity Falls. He is a very charismatic dream demon who wants to destroy the world by causing a rift between the Nightmare Realm and the real universe. also he officially appears as a recurring character in the simpsons shown in the episodes barts in jail and homer's adventures through the windshield glass Bill Cipher is the main antagonist of Disney's Gravity Falls. He is a very charismatic dream demon who wants to destroy