Underfist: Halloween Bash

Underfist Halloween Bash otherwise known as Underfist is an animated spinoff special of The Grim Adventures of Billy amp Mandy. It aired on October 12, 2008. The special was going to be the setup for a new series spinoff of Grim amp 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 amp Evil franchise, leading the show to be cancelled.

When the candy level gets too high, Hoss clicks his car unlock system, which causes a giant saw car spoof of the Gotengo from Godzilla Final Wars to drill out of the ground. They escape and devise a plan to attack the Underworld.Soon they find a portal to the Underworld in the rain, Hoss and Irwin jump in first but the portal turns off, because it is controlled by a diamond, which Mindy in her witch form smashes. The candy warriors try to sacrifice Hoss, by pushing him into hot coco, but they want to leave Irwin alive. This is because he has the powers of a mummy, which they need to keep the balance of the Underworld in place, and to become stronger warriors to eat the trickortreaters. ........

Source: Wikipedia