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Dee Dee is the older and caring, but slightly ditzy, sister to Dexter. 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 Koosalagoopagoop (Koosy for short) who lives in the land of Koos.
War Against Fuse
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. Even though she can't be found in the Future area, she is in Dexter's house as said by Dexbot Q-33.
The PastIn the Past, she can be found near Dexter's old house in Genius Grove. She has apparently inherited the house from her parents, who fled to Tech Square. 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). The monsters are trying to tunnel into Dexter's old lab to get his tech. Dee Dee doesn't seem to care about Dexter's lab and only tells the player to stop them because they're trampling her garden or taking the head of her doll. 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. 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.
Saving the Kids
Later missions given out by Dee Dee have you saving the kids of Endsville and Habitat Homes from Fusion Fuzzy Lumkins and Fusion Numbuh Three. The player is able to take down Fusion Fuzzy with help from Professor Utonium and they defeat Fusion Numbuh Three in Charles Darwin Middle School.
Mandark's Fusion Crush
Dee Dee finds out that Mandark stole Dexter's power wrench. The player takes Koosalagoopagoop to Mandark Industries' data banks to steal Mandark's data in order to find out what he's up to. Dee Dee discovers that her Fusion tricked Mandark into stealing Dexter's wrench. The player goes back to Tech Square and uses Koosy to enter Fusion Dee Dee's lair. The player defeats her and Mandark realises he was tricked. The player returns Koosy to Dee Dee and she gives them a reward.
Goggles based on her alter ego Diva Dynamite from the Dexter's Lab episode "Star Spangled Sidekicks" are a possible drop from defeating fusion monsters. There are also a line of ballet shoes based on hers that are acquired in the same way. A set based on another one of her alter egos, Racer D, from the episode "Mock 5" is obtainable, along with a hovercar.
Pieces of an entire set based on Diva Dynamite is obtainable by doing Infected Zone Races at Mandark's old house in the Past.
- 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).
- Fusion Dee Dee does not wear stockings, even though the real Dee Dee and her nano do.
- The Nano Power "Way of the Dee Dee" is a reference to the Dexter's Lab episode of the same name.
- The description for the Diva Dynamite Cape ""No capes!" is what Dexter says, which is why Dexstar is way lamer than Diva Dynamite." is a reference to the most famous quote made by Edna Mode, a character from Pixar's The Incredibles.
- On August 5th 2019, Dee Dee received a new character model in Retro Beta Patch 2.10