Dexter and Koos must save Peepers to keep the land of Kooz from disappearing. However, they must contend with a villain who is determined to make the land of Kooz disappear forever.
Dexter, Monkey, Agent Honeydew, the Justice Friends, Dee Dee, her imaginary friend Koosalagoopagoop, Mandark, his parents, and Dexter’s parents participate in a cross-country race a la Wacky Races.
Dee Dee accidentally shuts down Dexter’s lab, and he has to power it back. In the process, Dee Dee attempts to keep Dexter from finding out what she really did.
Monkey encounters Simion (Maurice LaMarche), an intelligent anthropomorphic chimpanzee who seeks vengeance on humans for turning him into his current state.
Loading the player... Dexter decides to work with Mandark, but finds himself doing all of the work. In the end, Mandark tries to press the button when Dexter connects the plug in the outlet to bring his show title back.
Dexter and Dee Dee listen in on their parents’ conversation; they are playing Scrabble, but the way they talk makes it sound like Dad was cheating on Mom
Dee Dee and her friends, Lee Lee and Mee Mee, enter Dexter’s lab and wreak havoc. Dexter clones himself to stop them, but the girls too make clones of themselves.
Dexter makes his own Major Glory action figures so that he can join the neighborhood’s Major Glory gang, but gets into serious trouble when the rest of the gang finds out that none of his action figures are original.
After Dee Dee declares that she can beat Dexter in any game, Dexter challenges her to a series of games in his lab, though he prefers to win by cheating.
In a fit of rage, Dexter dumps Dee Dee’s favorite teddy bear into the garbage. An upset Dee Dee begins to behave oddly, prompting Dexter to go to the garbage dump and get it back.
Not interested in hearing Dee Dee’s long-winded story, Dexter gives her a silencing formula to keep her quiet, but it instead turns her into a giant monster still bent on telling her story. When he realizes that nothing can make her quiet, he becomes a giant monster himself.
When his television show is interrupted by the Emergency Broadcast System, Dexter sets about fixing any emergencies in the neighborhood to make the signal go away.
Dee Dee’s stuffed animals come to life and roam the house when Dee Dee uses a formula that brings inanimate objects to life, which delights Dee Dee, much to his dismay.
Dexter finds the exact opposite of his family, a hyperactive boy who is like Dee Dee and has scientist parents who are like Dexter. Sensing to fit in, he switches places with the boy.
When Dexter is asked to bring his mother to school, he disguises Dee Dee as her so that she can take her place, but Dee Dee does not behave like their mother.
Dexter tries to prove to Dee Dee that Santa Claus is not real and is in fact their father in disguise. He ends up paying for his mistake when he has captured the real Santa Claus.
