Eines Tages sieht sich Dexter gleich drei vollkommen unerbetenen Gästen in seinem Labor gegenüber, als Mee Mee und Lee Lee seine Schwester Dee Dee besuchen. Als ob das nicht schon reichen würde, entdecken die neugierigen Mädchen eine Erfindung Dexters – einen Apparat, der Menschen klont …

Verzweifelt sucht Dexter eine Erfindung – doch sie ist ihm wohl endgültig abhanden gekommen. Es sei denn, Dee Dee hat sie in ihr Zimmer verschleppt. Mit größter Mühe überwindet Dexter seine Angst, diesen Raum zu betreten. Erwartet ihn dort tatsächlich die Krätze?

Ein Exemplar des ausgestorbenen Dinosauriers T-Rex erhält eine zweite Chance, als Dexter es mit einem Hundehirn versieht. Dee Dee freut sich sehr und geht mit dem Tier im Park spazieren. Derweil gerät Dexter mächtig ins Schwitzen als er versucht, das Wesen wieder einzufangen …

When his mother falls ill, Dexter creates a robot to do her chores. Dee Dee gets hold of its remote control and wreaks havoc, forcing Dexter to create a second robot to counter Dee Dee's.

Major Glory von den „Justice Friends“ sucht einen Helfer. So veranstaltet er ein Casting, ist jedoch mit keinem der Bewerber zufrieden. Erst die verkleidete Dee Dee beeindruckt ihn …

Dexter hat sich mit seiner Babysitterin nicht nur abgefunden, sondern sich sogar in sie verliebt. Als sie telefoniert, erfährt er zu seinem Schrecken, daß sie einen Freund hat. Dexter ist zu allem bereit …

Im Schlaf zu lernen ist eine wunderbare Sache. Doch als Dexter einen Apparat entwickelt, mit dessen Hilfe ihm das Französische wie im Traum zufliegt, bleibt die Kassette hängen …

Dexter verschenkt seine Schwester Dee Dee an ein paar Außerirdische. Nach einer kurzen Zeit der Erleichterung quält ihn das Gewissen und er zieht los, um sie zurückzuholen.

Nach dem Geschmack von Dee Dee ist Dexter deutlich zu verkrampft und soll lockerer werden. Doch das endet in der reinen Zerstörung …

Bei Reparaturarbeiten im Haus stoßen die Mitglieder der „Justice Friends“ auf einen tierischen Mitbewohner …

Banned from watching a late-night movie due to his young age, Dexter uses his technology to artificially grow into adulthood, but Dee Dee tampers with his machine, causing Dexter to turn into an old man.

Als Dexter und sein Rivale Mandarker auf einer Wissenschaftsmesse ausstellen wollen, fehlen diesem die Mittel. Mandarker nimmt Zuflucht zu schwarzem Zauber, um Dexter zu schaden.

Dexters Ballonanzug geht zu Bruch als Dee Dee damit fliegt und weggeweht wird. Am Ende repariert sie den Anzug zwar, doch eben mit ihren stark eingeschränkten Mitteln. Dexter ist entsetzt …

Rerun of "Dexter's Laboratory", the first "What a Cartoon!" pilot.

To clone a dinosaur with an incomplete DNA sequence, Dexter uses his dog's genetic code to fill in the gaps.

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

Due to overworking his brain, Dexter's mind shuts down, making him act idiotic.

After Dee Dee steals his critical invention, Dexter ventures into her room to find it.

Monkey encounters an alien hunter named Huntor and must fight him to save Agent Honeydew and Commander Chief.

Rerun of the second "What a Cartoon!" pilot.

Dexter and Dee Dee enter tryouts to become Major Glory's sidekick. When Dee Dee wins, Dexter realizes that fancy costumes are not the only criterion to become a superhero.

With only one television in their apartment, Major Glory, Krunk, and Valhallen disagree on what to watch: Major Glory's televised capture of the Disgruntled Postman, TV Puppet Pals, or the monster truck pull.

Dexter and Dee Dee's father buys a video game for them to play, but the game sucks Dexter inside when he plugs in the cartridge, and it is up to Dee Dee to bring him out.

Dexter has a crush on his teenage babysitter Lisa. When he finds out that she has a boyfriend, he sabotages their relationship and accelerates his age by ten years in an attempt to win her heart.

Valhallen loses his magic ax and starts turning into a nerd, forcing Major Glory and Krunk to enter his room to find it.

When Dexter's nightmares become frequent and problematic, he invents a machine that allows him to have nice dreams, as long as Dee Dee can operate it properly while she is awake.

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.

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

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".

Dee Dee teaches Dexter how to live life her way instead of being lonely and purely focused on science.

Major Glory forces Krunk and Valhallen to tidy up their apartment for his Uncle Sam, who is coming over for a visit.

To learn more about girls, Dexter camouflages himself and enters Dee Dee's room, where she is having a sleepover with her friends Lee Lee and Mee Mee. He gets caught by the girls, who force him to take part in their activities.

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.

To fix their apartment's plumbing, Krunk and Valhallen go to the basement, where they meet Ratman, a diminutive vigilante raised by rats (a parody of Batman).

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.

Major Glory, Krunk, and Valhallen try to rid their apartment of a bee.

Dee Dee inflates Dexter's hydro-plasmatic suit and constantly floats in the air, prompting Dexter to bring her down.

After fellow Justice Friend White Tiger helps Valhallen stop a super-villain, the latter invites him to spend the night in his apartment, forgetting that Major Glory is allergic to cats.

Not interested in hearing Dee Dee's long-winded story, Dexter gives her a silencing formula to keep her quiet, but it instead turns her into a giant monster still bent on telling her story. When he realizes that nothing can make her quiet, he becomes a giant monster himself.