Bill Cipher is an upcoming character who was confirmed by a number of hints; one of them being an animated picture of him posted on the Epic Rap Battle Parodies Facebook page; another being that you can see Bill Cipher on Pee-wee Herman's wallpaper in Hugh Hefner vs Pee-wee Herman.
Information on the rapperEdit
Bill Cipher serves as the main antagonist for Season 2 of Gravity Falls. He is a triangular dream demon formerly existent only in the mindscape who wishes to gain access to the real world by breaking an interdimensional rift cast when Stanford Pines dismantled the Universe Portal. He has been running amok in Gravity Falls, Oregon, since being summoned by Stanford Pines over thirty years ago.
Cipher is known for his mysterious demeanor and sadistic humor. He has existed for at least trillion years and is known to possess people, or "pawns"; the first being Stanford, as well as his grand-nephew, Dipper Pines, and then finally time-traveler, Blendin Blandin. In Blendin's body, Cipher breaks the interdimensional rift and is let loose into the real world, bringing forth a cataclysmic event called "Weirdmageddon".