Dexter is an extremely intelligent boy (a self described "Boy Genius") who has been creating fantastic inventions since he was a baby. He considers Albert Einstein to be his greatest influence. He is normally in conflict with his sweet 15-year-old sister Dee Dee. Dexter, though highly intelligent, often fails at what he has set out to do
Dee Dee is Dexter's extremely ditzy, simple-minded, energetic, hyperactive older sister, who inexplicably makes "squishy" sounds with her feet on every step. She usually, in one way or another, sabotages his experiments and destroys the lab every time.
Dexter's arch-nemesis. Approximately equal in intelligence to Dexter, he too possesses his own laboratory, which has a very black-and-red color scheme to make it look more evil and may be organic-based. It also is sphere shaped, opposing the design of Dexter's Laboratory.