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.
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 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.
After Dexter’s pencil rolls to the back of the school bus, Dexter goes to retrieve it, but legend says that no one has ever returned from the back of the bus.
Dexter’s parents discover that he is making false excuses to get out of physical education and now Dexter must pass a physical exam if he wants to pass P.E. and move up a few grades.
When Krunk gets a tortilla chip stuck in his tooth, Major Glory decides to fix it by pulling the tooth out himself against Valhallen’s admonition to take him to the dentist as they have the tools to take the chip out properly.
Dee Dee dares Dexter into building her a giant robot similar to his Robo-Dexo 2000. They then team up to try to save an island’s population from being destroyed by an erupting volcano using their giant robots.
On Mother’s Day, Dexter’s mother has her gloves taken by the family so that she can relax and not do housework, but she is unable to adjust to a life where she cannot keep the house clean.
Dexter finds a lost Labrador Retriever, but when he teaches the dog to speak human language, he turns out to be very annoying, prompting Dexter to find the dog’s owner.
Dexter invents a robot parrot that happily repeats self-congratulatory comments he makes, but when it starts repeating things about his lab and escapes, he sets out to destroy it before it tattles to his parents.
Suspicious that Dee Dee has not entered his lab even once on a particular day, Dexter shrinks himself and enters her room to spy on her. He soon becomes an unwilling character in Dee Dee’s doll story, but he believes the story to be real.