In Sdrawkcab/The Continuum of Cartoon Fools/Sun, Surf, and Science (1998), Dexter speaks backwards a few times. When he keeps falling up and down, he says "That was close" in reverse. After Mom yells at him for expecting him to take out the trash, he says "I did!" in reverse.
This episode was produced as the 36th but aired as the 33rd episode in the second season.
In a rare moment, Dexter gets to punish Dee Dee from aggravating him. Using the reverse belt, he puts her in a loop of falling to and from the floor; listening to her scream in terror.