The special was going to be the setup for a new series spin-off of Grim & Evil, but Maxwell Atoms's contract with Cartoon Network expired before he moved to Disney Channel for the TV series Fish Hooks, and the special was ultimately the finale of the Grim & Evil franchise.

Billy, Mandy, and Grim decide to go home after having no success with Dracula, who rudely hands them pennies.

The candy warriors try to sacrifice Hoss by pushing him into hot cocoa, but they want to leave Irwin alive.

He also reveals that he cut off Fred's tusks, made Billy scared of spiders, and haunted Hoss's childhood.

Grim, Billy, and Mandy (who became president) award Underfist for saving Halloween, but then they hear something outside and investigate.

Maxwell Atoms started production on Underfist shortly after he finished with The Grim Adventures of Billy & Mandy.

Cartoon Network did not pay for a permanent crew for a single film, so much of the work was done freelance or by Atoms himself.

[1] The special did not become a series due to the fact that Cartoon Network's president at the time Stuart Snyder chose to focus on new ideas, which included live–action.

[3] Underfist tied for first in ratings for the week it was aired and was nominated for Best Animated Television Production for Children in the 36th Annie Awards.