Dee Dee is Dexter's extremely ditzy, simple-minded, hyperactive older sister. According to the Photo Day Episode, she is in the 6th grade.. She usually, in one way or another, sabotages his experiments and destroys the lab in every episode of the show, even though she seems to show care or love for her brother. Dee Dee also loves ballet, puppies, unicorns, playing dolls with her friends, messing around in Dexter's laboratory and generally depicts all the stereotypes concerning normal girl activities.
Dee Dee sometimes visits the cyberchase fighters to see dexter and sometimes she goes on adventures with them
Although she seems to be extremely ditzy, her social skills far exceed Dexter's, as she is quite popular at their local school while he is shunned except for his other equally geeky associates. Her best friends in the series are Mee Mee and Lee Lee two 15-year-old girls that share her interests, even though they are noticeably different in appearance. Her catch-phrase is "Ooooooo, what does this button do?". She wears her full length of hair down on rare occasions, mostly when sleeping. She also has a multitude of stuffed animals and she has a four poster bed. It was revealed in the episode "A Hard Day's Day" that Dee Dee is a Cancer.