18 Weirdmageddon Part 1

The ultimate battle for the fate of the world begins as Bill Cipher and his "friends" are released from their dimension. Meanwhile, Dipper and Wendy try to save Mabel from a prison bubble designed by Bill and guarded by Gideon. Guest stars: Louis C.K. as The Horrifyingly Sweaty One-Armed Monstrosity[note 4], Danielle Fishel as Pyronica, Patrick McHale as Hectorgon, Andy Merrill as Teeth, Brian Bloom as Rumble McSkirmish, Nathan Fillion as Preston Northwest, Justin Roiland as Blendin Blandin, Dave Wittenberg as Time Baby and Lolph, J. K. Simmons as Stanford Pines Note: Jason Ritter and Linda Cardellini also appear briefly as Dipper and Wendy (respectively) in a live-action shot.