Trivia / Underfist

• Billing Displacement: The credits list the actors for the main characters from Billy and Mandy, Grey Delisle (Mandy), Greg Eagles (Grim), and Richard Steven Horvitz (Billy), before the actors for the titular team.
• Keep Circulating the Tapes: The Latin American Dub for the special was believed lost for years up until June 27, 2021 thanks to being found by a user in Lost Media Wiki, then uploaded and backed up online, and later on this was finally dealt with for good thanks to HBO Max officially uploading the dub in their platform's Latin American version.
• Screwed by the Network: While there were plans for at least two more specials, Maxwell Atoms' contract with Cartoon Network ran out midway through development on Halloween Bash; management didn't feel it was worth renewing it, so the concepts were shot dead in the water.
• Stillborn Franchise: There were plans for a series and potentially two more specials, but Cartoon Network's management weren't interested.
• What Could Have Been:
  • The special was meant to lead to a spinoff series. Maxwell Atoms would share the full pitch bible shortly after the TV movie's release, and later reveal that two of the supposedly joke specials seen during the end credits would have been actual episodes:
    • The first, Underfist -vs- The Dinosaurs, was about Hoss and Eris' relationship; after Hoss broke up with her, Eris' turmoil and heartbreak caused her to split into two, becoming Naughty Eris and Nice Eris. The two would fight for his affection with armies of dinosaurs trying to prevent their own extinction.
    • The second, Underfist: Against the Astro-Vampires, was about Underfist going into space, discovering Dracula's otherworldly origins, and encountering Nephthys, Egyptian Goddess of Mourning and daughter of Anubis, who was determined to put Irwin in a tomb — she's the one blasting lasers at a motorcyle-riding Irwin in the credits.
  • Jack O’Lantern was supposed to make a cameo in Halloween Bash… as a scarecrow◊.
  • When talking about plans for the show, Maxwell Atoms revealed the team would have sometimes been shaken up, with Eris temporarily replacing Hoss at some point, and Jack O'Lantern also could have been a potential member of the team.

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