|“||Ooooh! What does this button do?||”|
Dee Dee is the older and caring, but slightly ditzy, sister to Dexter and is the clumsy fool that caused the player to go too far into the future at the game's start. Even though she seems a bit dim and not as bright as her brother, she still loves Dexter. Her favorite doll is the Ponypuff doll, her best friends' names are Mee Mee and Lee Lee, and she utterly hates Mandark, even when she knows that Mandark likes her. She has an imaginary friend called Koosalagoosagoop (Koosy for short) who lives in the land of Koos.
In FusionFall, Dee Dee is the one that caused the player to go too far into the future at the game's start by pushing a button on Dexter's Time Machine. She has apparently inherited the house from her parents, who fled to Tech Square. Her Fusion is found within the Genius Grove infected zone, which is Mandark's old home. Due to her ditzy nature, she mistakes her Fusion for a ballerina monster. In The Future, even though she isn't found, she is in Dexter's house as said by Dexbot Q-33.
Most of Dee Dee's missions involve taking out monsters around the Genius Grove area, but she has her parts in other characters' missions (such as one that involved one of the Kanker sisters). Despite the fact that Dee Dee knows she helped cause the problem with the player in the beginning, she never really talks about it if the player talks with her. She has two best friends who are near exact twins of her, Mee Mee and Lee Lee, and neither girl has been mentioned by Dee Dee or anyone else, hinting that Fuse might have gotten to them already. Dee Dee mentions she has an imaginary friend, Koosalagoosagoop, but he was never seen or made in the game.
- It is believed that in The Future , Dee Dee still thinks Dexter is alive and is waiting for him at home (as said by Dexbot Q-33 earlier in gameplay).