Dexter reluctantly takes piano lessons from Professor Williams (Paul Williams), but when the Professor stumbles onto Dexter’s lab, he discovers that Dexter has more musical talent than he thought.

When Dexter cannot get the ice cream truck to stop for him, he creates a series of obstacles to do so.

Dexter’s mother asks him to read a story to a sick Dee Dee. Dee Dee becomes bored of Dexter’s story and creates one of her own.

Quackor returns to battle Monkey in Dexter’s Lab until Quackor lays an egg; then the two fall in love.

Dexter’s family goes to the beach, where Dexter tries to communicate with whales. He must rescue Dee Dee (dressed as a mermaid), when she is captured by manic pirates.

Old Dexter And Old Dee Dee’s talks about the glory days, and his sister is still there to inject her opinions, telling him what really happened.

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

After a crime prevention talk at school, Dee Dee, Lee Lee, and Mee Mee become crime fighters, but they unintentionally end up being neighborhood criminals.

When Dexter uses anti-matter on the family car to shorten road trips, he accidentally fuses Dee Dee with the car.

Tired of bathing, Dexter laminates himself to stay clean.

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 “fires” Dee Dee, only to realize that the chaos she causes has been helping him concentrate.

Dexter tries to make himself and Dee Dee older to see an R-rated movie, but he accidentally makes everybody else babies instead.

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.

Dexter is trapped in his school by the janitor in revenge for making him work late everyday due to Dexter’s habit of leaving the school last everyday.

Dexter and Dee Dee protect their mother’s muffins from their muffin-loving father while she is out shopping.

Dee Dee’s imaginary friend Koosalagoopagoop (Dom DeLuise) suddenly comes to life and starts annoying Dexter.

Dexter and Dee Dee realize that they make a good team, so they decide to do stuff together, but doing so makes things worse.

Dexter’s mom fights another woman at the supermarket for some new latex gloves.

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.

Monkey encounters Simion (Maurice LaMarche), an intelligent anthropomorphic chimpanzee who seeks vengeance on humans for turning him into his current state.

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.

After Dexter orders and eats a giant burrito, he suffers severe stomach pains. Believing a test the computer gave him, he assumes that he has only 30 minutes to live.

Dexter brings the cavemen who first discovered fire back from the past, who acts like Dee Dee and starts smashing the lab.