|Underfist Versus the Dinosaurs|
Underfist: Halloween Bash
Underfist versus the Dinosaurs was said to be a sequel of Underfist . It was only seen in the credits where Hoss fights a Tyrannosaurus with Nice and Mean Eris on it and Irwin fights a Pteranodon. During the song, the Underfist truck gets chased by a Ceratosaurus.
According to Maxwell Atoms, this episode is about Eris (who has been absent from the series since the episode Chaos Theory) who turns out to be heartbroken from her breakup with Hoss and when her heart split in two, so did Eris and transforms into two versions of herself, Nice Eris (who tries to woo Hoss to being the perfect girlfriend) and Naughty Eris (who tries to challenge Hoss with her bad girl intentions) and they are leading an army of dinosaurs trying to prevent their own extinction and Underfist has to travel back to prehistoric times to defeat them.