When a team of robots from the future bursts into Dexter's Laboratory with the intention of destroying "the one who saves the future," Dexter assumes they are referring to himself. His curiosity ends up getting the best of him as Dexter uses his time machine and visits himself at different stages of his life to piece together exactly how he saves the future. At each trip, Dexter goes face to face with his arch enemy, Mandark. Towards the end of the journey, Dexter must help Dexter, Dexter, and Dexter from the the evil Mandark and save the future.

Dexter finds himself in a post-apocalyptic future, and running it is a power hungry, now obese Mandark! Dexter (with pimply teen Dexter, buff hero Dexter, and senile old Dexter) must face the original Mandark (with Mad Scientist Mandark, Fat Mandark, and Disembodied Brain Mandark) to save the future. Ah, what a fine day, for science!

The film premiered as part of Cartoon Network's Cartoon Theater on December 10th, 1999, a nice way to kick off the millennium. It served as the last time the original cast would assemble to create Dexter's Laboratory. Ego Trip was directed by Genndy Tartakovsky, the creator, and featured the voices of Christine Cavanaugh as Dexter, Kathryn Cressida as Dee Dee, and Eddie Deezen as Mandark. The art direction was even done by the now infamous Craig McCracken of The Powerpuff Girls fame. Currently Cartoon Network still airs this film as part of its Cartoon Theater features. It is also available on video from Warner Bros. Home Video.