Nice Eris & Naughty Eris were supporting antagonists of Underfist: The Series, the cancelled spin-off show of The Grim Adventures of Billy & Mandy series, and were going to be the main antagonists of the 2009 cancelled movie Underfist versus the Dinosaurs.
Two psychotic halves of the original Eris, the Goddess of Chaos, Nice Eris and Naughty Eris would have been created due Hoss Delgado's break up with Eris, leading them to try to get back at Hoss for what he did to their original counterpart, becoming rogues of the Underfist superhero team in the process. They were going to be Hoss Delgado's archenemies.
They were presumably intended to be voiced by Rachael MacFarlane as their original counterpart.
After finishing The Grim Adventures of Billy & Mandy, Maxwell Atoms started to work on Underfist: The Series, a new television show for Cartoon Network. Planning it as an spin-off of the series, featuring Irwin, Hoss Delgado Jeff the Spider, Fred Fredburger and General Skarr in the lead roles, Atoms decided to make a pilot movie entitled Underfirst: Halloween Bash. With the movie's Halloween 2008 release date still waiting, Atoms began to plan the characters for his newest show, and among them, he created the rogues whom the Underfist superhero team would have to face. Two of them were going to be Nice Eris and Naughty Eris, and as a result, were included making cameos in the pilot movie's end credits.
According to Atoms' notes, Nice Eris and Naughty Eris would have been created when Eris, a recurring antagonist of The Grim Adventures of Billy & Mandy, breaks up with Hoss Delgado in the show's sixth season (specifically in the episode "Chaos Theory"). As a result, out of desperation, Eris ends up splitting into two halves, one named Nice Eris and the other named Naughty Eris. They were set to get back at Hoss for what he did to their original counterpart.
Nice Eris was going to be Eris' romantic part. Having blond hair tied with a bun and wearing a white girego style dress, Nice Eris constantly tries to be the perfect girlfriend to the point of being considered a nuisance, as she just wants to be loved by all as the embodiment of suffocating love. Conversely, Naughty Eris was going to be Eris' bad part. Having black and loose hair and wearing a wild dark blue dress, Naughty Eris is the typical bad girl who listens to loud music and usually plays video games or eats ice cream at night, wanting Hoss to participate in her antics, which don't bring good intentions at all.
Aside their role as supporting antagonist in Underfist: The Series, Nice Eris and Naughty Eris were going to be the main antagonists of the 2009 planned movie Underfist versus the Dinosaur, the sequel to Underfist: Halloween Bash. Judging from the scenes seen in the pilot movie's credits, Nice Eris and Naughty Eris were going to ride a dinosaur at one point and Eris' iconic Apple of Discord would have been involved in the plot. According to Atoms, the film's plot had Nice Eris and Naughty Eris leading a dinosaur army in the prehistory to avoid their extinction, leading Underfist to travel to the past and stop them.
Unfortunately, despite all his plans for the show, Maxwell Atoms was ultimately unable to carry them out because his contract with Cartoon Network expired in 2008, aside that Stuart Snyder, the network's newest president, desired to have more live-action shows in Cartoon and no spin-offs, leading to what eventually became known as Cartoon Network's Dark Age. This consequently led Underfirst: The Series to be cancelled and left Underfist: Halloween Bash as the finale of the Grim & Evil franchise.
- It's possible that Nice Eris and Naughty Eris were inspired by the Greek poet Hesiod's description of Eris on his didactic poem Works and Days.
- Nice Eris was the only one of the two who closely resembled the original Eris.