Mandark brings his lab duck Ducky for show and tell to counter Dexter and his lab monkey. Though neither creature displays remarkable characteristics at school, Ducky, unbeknownst to Mandark, is the alter ego of supervillain Quackor the Fowl.

Mandark’s birth and origins as the child of hippies are revealed, as is the beginning of his rivalry with Dexter and the cause of his villainy.

While out for dinner at a pizza restaurant, Dexter tries to slow down the “Whack the Weasel” machine to win a stuffed Monkey doll before Dee Dee does. Security captures him for tampering with the machine, and he falls into the hands of a mad scientist.

After a Puppet Pals marathon, Krunk dreams the Puppet Pals are attacking puppet versions of Major Glory and Valhallen.

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.

When Dee Dee befriends a turtle that gets severely injured, Dexter not only heals it, but gives it superpowers.

Dexter and Mandark are both outperformed by a new girl at school, so they reluctantly team up to get rid of her.

When Dee Dee tries to cut off a piece of her hair, she accidentally cuts off one of her pigtails. Dexter gives her a potion to make her missing hair grow back. However, Dee Dee squirts too much of it in her hair, and Dexter must return Dee Dee’s hair back to normal.

Dexter studies the potato, and when he is fascinated by its power to light up a light bulb, he tries to use it as an energy source.

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.

To keep himself from forgetting anything important, Dexter uses a device to copy his memories, which causes a mayhem in his own head.

Dexter’s mother attempts to support him during a chess tournament but does nothing but embarrass him.

Dexter’s new device allows him to study for the next day’s French test while sleeping. It malfunctions, causing a single phrase (omelette du fromage) to repeat throughout the night, causing Dexter to wake up the next morning speaking nothing else except omelette du fromage.

Dexter thinks that a crazy homeless person balancing electronic devices on his head and muttering gibberish is a genius trying to contact aliens, so he takes him home.

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

Dexter tries to emulate the barbarian hero of his favorite comic book.

Dexter’s father tries to watch a golf tournament, but is constantly interrupted by his wife, Dexter, and Dee Dee.

Dee Dee goes and plays in her own “lab” after being kicked out of Dexter’s.

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

When Dexter cannot reach anything in his lab, he makes himself more flexible by combining himself with bubble gum.

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

Dexter and Dee Dee go to South America to catch the legendary chupacabra.

In this crossover with Dynomutt, Dog Wonder, Blue Falcon (Gary Owens) comes to Dexter’s house and asks him to rebuild an injured Dynomutt.

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

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.

Dexter and Mandark drill underground to expand their labs, but end up running into each other’s work. So they agree to share the lab, inducing chaos.

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 Dee Dee eats a contaminated apple, she turns into a monster every time when she tells Dexter what to do.

When his family is suffering from the flu, Dexter tries his best to not acquire the illness, but his efforts are thwarted by a sick Dee Dee’s presence in his lab.

Mandark Astronomanov, a new student at Dexter’s school, seems to be superior to Dexter academically. Mandark forces Dexter to shut down his lab so that Mandark’s lab can gain more power. However, with the help of Dee Dee, Dexter manages to destroy Mandark’s lab.

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.

Mandark plans another scheme to get rid of Dexter. Everything in this cartoon is to the tune of Mandark’s trademark laugh.