The Continuum of Cartoon Fools is the second part of the 33rd episode in season 2 of Dexter's Laboratory, which first aired on April 1, 1998. In this episode Dexter tries to find out how Dee Dee keeps getting back into his lab after he kicks her out. Overtime, it drives him crazy and he seals the lab to make sure that Dee Dee doesn't get in again. In fact, Dee Dee is not doing anything fun today, only for Dexter to find out that he can't access his lab.
Dexter is inside his room writing on a test paper and testing how he is distracted. Dee Dee enters his room with a dynamite pack and enters Dexter's lab. This distracts Dexter and he looks around and sees if he pressed a button. He shakes it off and goes back to writing. Dee Dee opens the lab again, and Dexter looks under his desk. Dexter then watches as Dee Dee passes a laser eye check. He then goes after Dee Dee. Inside the lab, Dexter pushes Dee Dee out from the rug entrance and he shoots it shut. Back inside the lab, Dexter finds Dee Dee screwing in a bolt and yells at her. Dee Dee shows him how she got in. She pushes the button on a remote and it sends Dexter to a mountain range where a man is yodeling into an alphorn. Dexter uses his transporter remote to bring Dee Dee into the mountain range. He grabs the remote out of her hands and smashes it into the ground, and teleports back home using his remote. There, Dexter destroys his remote, and sees Dee Dee walking into his lab.
Dexter, for the third time, asks Dee Dee how she got in. She whispers her answer to him and sends her into a fridge. Dexter then orders Computer to close a series of doors, and has her hang a small sign that says "Think thin!". Later, Dexter is working on an experiment and Dee Dee is helping him. Dexter passes her his atomizer and they both scream. Fed up, Dexter starts asking Dee Dee how she got into his lab, and with every failed attempt, she keeps reappearing. Dee Dee tells Dexter how she really got into her lab, so she is not doing anything fun today, she was only making some minor adjustments in Dexter's secret lab, and Dexter locks the lab and swallows the key. Dee Dee tells him the truth, and Dexter realizes what he has done.
This episode could explain how Dexter limited his entrances to the lab by getting rid of all the other possible entrances. Hence the later episodes mainly showed his entrance to the lab soley by the bookcase entrance.
Though Dexter locks himself and Dee Dee out of his lab...he regained access to his lab as the series continues, exactly how is unknown.
A boltcutter or blowtorch from the garage is not out of the question.
Dee Dee is not doing anything fun in this episode.
There was even a text that said "A Hanna-Barbera Cartoon" in the title card.
The episode is a reference to the endless cycle of slapstick shenanigans and failures that occur within cartoons that ensures that the "fool" of said toons will never be able to succeed at getting the best of their counterpart.
The episode's title card is reminiscent to the flat and simplistic style title cards used in various early Hanna-Barbera television cartoon shorts of the 1950s and 1960s such as Yogi Bear, Huckleberry Hound, Pixie and Dixie, Quick Draw McGraw, etc.