In need of an assistant to operate his latest invention, Dexter performs a brain transplant on Dee Dee to make her smart enough to fulfill the role. With her new brain, Dee Dee proves to be more intelligent than Dexter.
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.
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.
When Dexter’s new device, made to help him see through solid objects, fails to work as expected, he ends up seeing through people’s clothes, which puts him in an uncomfortable situation.
After staying up late at his lab, Dexter oversleeps, waking up one minute before his school bus arrives. With no time to do his morning chores and homework, he pulls out a secret prototype device, which converts his last 30 seconds into 30 minutes.
When Dexter is bitten by a clown’s dentures, he begins turning into a mad clown every night, terrorizing the town with his mayhem, and only Dee Dee, who knows mime, can stop him.
Dexter’s lab is threatened with repossession unless he can repay his debt to NASA. When Dee Dee wins the same amount in a lottery, he decides to steal her money out of desperation.
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.
To prevent himself from being taken away by aliens for experimentation, Dexter tricks Dee Dee into going instead, but he regrets his decision after realizing how much he cares for her.
Dexter is forced to take Dee Dee to the zoo. There, she ends up trying to save an ostrich with disastrous results. Dee Dee and the ostrich switches their places.
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.
Dexter is disappointed when he ends up at an Amish farm instead of a high-tech farm for summer camp. His attempts to modernize the Amish family do not go well.
When Dexter tries to inject himself into an ill Dee Dee to find a cure to the common cold, he accidentally ends up inside his dog, believing that Dee Dee is infected with a dog virus.
