I watched this for the first time after many years and was quite surprised as to just how many dark tones are really in this movie.
It more or less involves Dexter going into the future after some robots come back to the past to "destroy the one who saved the future." However, when he gets there, all is not well as Dexter sees that an alternate time-line has occurred in which his future self is a spineless wimp in the service of his lifetime rival, Mandark. Near future Dexter, Number 12, is reduced to doing to most menial and brainless tasks Mandark can think of, like designing new cubicles.
Under Mandark's control the near future is turned from a what could have been a great world into a dark dystopian future. Young Dexter is hailed by a passing robot and is about to get in trouble for "unauthorized walking" when his eye print identification is recognized and he is transported to his older counterpart's cubicle. From there he gets treated to the spectacle of seeing his older self publicly flogged by Mandark himself for being "almost late." This really stuck out in my mind, being almost late. Mandark can literally do anything in this world and time because nobody and nothing opposes him.
The rest of the movie goes on in a similar way, with a happy ending (it is after all a kids movie). One of Cartoon Network's better flicks, it came out in 1999.