Underfist: Halloween Bash (otherwise known as Underfist) is an animated spinoff special of The Grim Adventures of Billy & Mandy. It aired on October 12, 2008. The special was going to be the setup for a new series spin-off of Grim & Evil, but the contract of Maxwell Atoms with Cartoon Network expired before moving to Disney Channel for the TV series Fish Hooks and the special was ultimately the finale of the Grim & Evil franchise, leading the show to be cancelled.