Dexter's Laboratory: Ego Trip is an animated film based on the Cartoon Network animated television series Dexter's Laboratory. It was produced by Hanna-Barbera (now Cartoon Network Studios) for Cartoon Network and originally aired on December 10, 1999. The special follows Dexter, the series' protagonist, as he travels forward through time and meets futuristic versions of himself and his rival Mandark.
Originally intended to conclude the series, the film maintained successful ratings for the channel, despite mixed reviews from critics; it led to Cartoon Network reviving the show for two more seasons in 2001, which began that year and concluded in November 2003.
After routinely chasing the evil Mandark (Eddie Deezen) out of his lab when he tries to steal the "Neurotomic Protocore", Dexter (Christine Cavanaugh) asks Dee Dee to leave the lab. She enters the time machine. Suddenly, Dexter is confronted with a group of robots that have appeared from his time machine. They declare that they are here to destroy the one who saved the future and make ready to attack Dexter. Dexter easily destroys them with the use of various tools and gadgets from his lab, as the robots do nothing except stand there while Dexter was fighting them. However, news that he is "The One Who Saved the Future" intrigues him, and he decides to travel through time to discover how cool he is.
In the first time period he visits, Dexter finds a tall, skinny, weak version of himself working in an office designing cubicles, with Mandark as his rich, successful and abusive boss. The child Dexter berates his older self for allowing Mandark to bully him around, before unwittingly revealing the existence of blueprints regarding the Neurotomic Protocore from the beginning of the movie, and Mandark steals it after the two Dexters move forward in time. In the second time period, the two Dexters meet their much older self, a wizened senior citizen Dexter about the same height as the child Dexter (and Mandark's brain in a vat who cannot do anything other than complain about his situation). All the technology from the blueprints has been implemented, creating a utopian society where anything can be materialized with the power of the mind. The old Dexter can't remember how he saved the world, so they travel back in time to find out.
In the third time period, which appears to take place between the first and second time periods, they find a dystopic world where everyone is stupid and fire and technology are forbidden, controlled by Mandark thanks to the Neurotomic Protocore. They meet action hero Dexter (Jeff Bennett), who is tall, muscular and bald (senior citizen Dexter, it turns out, wears a wig), fighting the evil. Hero Dexter explains that he and Mandark had been employed at a government research agency many years ago, and Mandark had stolen many of Dexter's ideas, and used them to rise through the ranks eventually taking over the company, reducing Dexter to the weakened cubicle designing employee from the first time period. Eventually, Mandark got ahold of the Neurotomic Protocore (the kid Dexter slaps the young adult Dexter for leaving it out). Mandark tried to employ the core's power, but he set the core's positive flow to negative, its energies sweeping the world, numbing the minds of the population, allowing him to take over the world, hoarding all science and knowledge for himself.
Dexter, no longer able to stand being enslaved and determined to stop Mandark, spent years digging underground to escape Mandark's tower, growing a large beard and huge muscles in the process. By the time he emerged, the world was in its current state. The four Dexters go back to Dexter's laboratory and build a giant robot to invade Mandark's fortress. Reaching there, they confront Mandark, now morbidly obese, with his only form of locomotion being carried around his lair by a hook-and-winch that connects to a hole in the back of his briefs. Mandark summons versions of himself from other time periods to oppose the Dexters. A battle royal ensues, with each Dexter fighting the Mandark of his own time period.
After a battle between the Dexters and Mandarks, Dexter almost reaches the button to save the world; however, Dee Dee (Kat Cressida) unintentionally saves the world by wandering in from the open time gate and pressing the button to reverse the waves of the Neurotomic Protocore, thus creating the utopian world, causing the dystopian Mandark to explode with only his brain intact, and the remaining ones to be teleported back to their own time periods. The Dexters, overcome with jealous rage at having their thunder stolen, create a group of robots and tell them to "destroy the one who saved the future", and send them back through the time machine to take care of Dee Dee, unwittingly setting the whole series of events in motion.
The Dexters return to their original time periods. Dexter returns to right before he originally left at the beginning of the film and sees himself fighting the robots he just built. Dexter becomes confused when he sees this, but he decides to ignore it and goes to eat lunch. When Dee Dee shows up, Dexter walks away because he's still angry that his sister stole his thunder. Dee Dee is confused.