Evil Jim comes across a device that allows him to create complete opposites of anyone. But when he attempts to use it to take on Earthworm Jim and his friends, Peter's transformations may finally come in useful.
Bob the Killer Goldfish invents a device that can transfer "evolution energy" from its target to its user. This devolves the target to a lower life form and takes Bob to a higher stage of evolution. Jim and Peter become its victims.
Psy-Crow forces the narrator to read that him and Professor Monkey-For-A-Head have overthrown Queen Slug-for-a-Butt, which automatically happens. Ethel Bleveridge takes her in. To stop them, Jim and Princess What's-Her-Name need her help.
Evil the Cat teams up with Malice the Dog, the love of his life. The villainous couple steals Jim's Hairpin of Destiny to summon The Fiend Which Dares Not Speak Its Name and destroy the universe and her Fleas of Eternal Slumber send Jim and his friends to the Realm of Nightmares.
Evil the Cat comes up with his final diabolical plan to destroy the universe when he learns of the prophecy that says that if the circumstances are right, a uniquely terrible singing duo could destroy the universe with their awful song. Lounge act Morty and Eileen fit the bill. Meanwhile, the Galactic Heroes' League deems that Peter's actions have saved the day much more often than Jim's, so they award Peter with Jim's suit. Peter becomes the new hero and Jim must find a new job. Also, Jim notices that the show's budget is running out.
Jim and Peter find themselves in an alternate world which apparently bears a striking resemblance to The Wizard of Oz. When Jim comes into possession of treasured Sapphire Toe-Socks, they must find a way back to their world before the alternate Queen destroys them.