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

Mandark gets in touch with nature.

Dexter accidentally gives himself telepathy that he cannot shut off when trying to overhear his father’s thoughts to figure out what he got for his birthday, causing everyone to accidentally read his own mind.

While fighting Comrade Red and his gang, Krunk falls in love with his equivalent in their gang, She-Thing (Kath Soucie).

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.

While on a date with Agent Honeydew, Monkey gets hypnotized by the music of the Organ Grindor (Jim Cummings), who commands him to rob Fort Knox.

Dexter is upset that Dee Dee is more photogenic than him, so he transforms his face into a handsome one for his next Picture Day.

Dee Dee wins a golden diskette, earning her a free trip to the laboratory of Professor Hawk (Tom Kenny), one of Dexter’s favorite scientists.

Mandark disguises himself as Dexter’s mom to get into Dexter’s Lab. Unfortunately for Mandark, he now has to deal with Dexter, Dad, and Dee Dee’s requests, which are too much for him.

Dee Dee gets a song stuck in her head, which is actually a virus. Dexter and Mom soon catch it, and Dexter has to reverse the effects of this. He succeeds at the end, not knowing that Dad also caught it.

Dee Dee’s father trains her to fight a gang of bicycle-riding rogues dressed as ninjas who target her paper route every morning.

Dexter falls in love with a new girl at his school, but he cannot win her heart until Dee Dee helps him with poetry

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.

Following a mishap in his lab, Dexter ends up in the old, long-abandoned part of the lab, and discovers his early, neglected inventions.

It is Career Day, and because Dexter is ashamed of his father, he creates a better father for himself. However, he soon discovers that his real father is much cooler.

Rerun of the second What a Cartoon! pilot.

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 and Mandark team up to fight asteroids that are heading towards the Earth.

Dexter becomes the stern administrator of his local library.

A teleporter malfunction sends Dexter to an alien prison, prompting Dee Dee to go on a mission to save Dexter.

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.

Mandark enters a surfing contest and tries to cheat his way to victory to win Dee Dee’s heart from another surfer.

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

Dexter and Mandark bring the Abraham Lincoln and George Washington faces respectively on Mount Rushmore to life and make them fight each other to determine who is the best.