|Aliases/Nicknames||Moron and Stupid Sister (by Dexter)|
|Family||Dexter (brother), Mom (Mother), Dad (Father), Grandpa (Grandfather), Fergle O'Reilly (Uncle), Dextamina (Great Aunt)|
|Occupation||Student, Ballet Dancer|
|Interests||Dancing, playing in Dexter's lab, girly stuff|
|First Appearance||Changes (on What a Cartoon)|
|Voiced by||Allison Moore, Kat Cressida|
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 in every episode of the show, even though she seems to show care or love for her brother. Though she was shown to get hypocritcally angry when she found that Dexter had been in her room and messed with her stuff. 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. Her catch-phrase is "Ooooooo, what does this button do?." She rarely wears her full length of hair down except 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's astrological sign is Cancer indicating that she was born somewhere between 21 June or 22 July.
Originally voiced by Allison Moore, the role was assumed by Kathryn Cressida after the first season. Moore reprized the role in the third season, with Cressida taking it back for the show's final season. Allison Moore seemed to portray Dee Dee as feeble-minded and innocent, while Kat Cressida portrayed her as being more annoying and excited.
She is two to three times taller than Dexter and has peculiar body proportions; a minuscule torso with a large head and gangly limbs, similar to a ballerina's. To complete the ballet look, she wears a rose colored small tutu, white tights and ballet shoes, which usually create a "squishy" noise while walking. She sounds like both her parents, has a similar personality and hair color to her father. For sleeping she wears a pink nightgown, and she wears her hair down. For swimming she wears a pink one piece swimsuit and a pink swimming cap with the initial 'D'. She has blue eyes and blonde hair in pigtails.
- Dexter - Dexter is Dee Dee's little brother. She loves "playing with," him but she destroys things in his lab and drives him crazy. It may seem that Dee Dee is nothing but a pure idiot who just annoys Dexter all the time, but truthfully deep down inside of her candy canes and lollipop glitter heart, she loves Dexter and thinks he's awesome. In fact, to her, Dexter is her favorite thing in the whole entire world. This was seen in the episode "Game Show" where the Game Show host asked what their favorite things in the world were and Dexter is what Dee Dee chose. When Dee Dee comes into the Laboratory, she never wants to destroy any of his inventions or ruin any of his experiments. What she really wants out of all that, is to spend time with her little brother Dexter and to spend time with him in their early years of that short and brief section of life called childhood. Dee Dee is really alot smarter than she comes on to be, Dee Dee is really a smart girl and she is smart enough to know that if Dexter doesn't get out of his lab more often and see the world, he will have wasted his life trapped inside of his lab. Sometimes she wants him to come outside which she does and clearly explains in various episodes such as Way of the Dee Dee. She wants him to see the world and realize what a wondeful and perfect thing life is and to have him experience the best things in life and alot of the time, Dee Dee's wreckless little antics are actually the things that make Dexter do those good things in life. It may be possible that she does this intentionally because she knows what the outcome would be, some would even say she is smarter than Dexter.
- Mandark - Mandark is madly in love with Dee Dee despite her extreme lack of intellegence. His love is so powerful for her that his dark and evil personality completely changes to a soft side wheneven he sees Dee Dee and he dazes off into a world of love and joy where he usually says a common cathphrase of his which is "Dee Dee" said in a slow and loving way. Mandark is head over heels for her and wants nothing more than for her to love him back and for the two of them to be together. Dee Dee however, on the other hand does not show the same affections back. Dee Dee is grossed out by him and despises him which is because she thinks he is unattractive for one but mostly because he hates her favorite person in the world, Dexter. Mandark is aware of this but he still can't let her go and is always following her around and bothering her. He seems to have so much time and love for her, he has an entire serine to her in his closet as seen in the episode Babe Sitter and he even sometimes builds Dee Dee related material on his robots and inventions as seen in the episode Let's Save the World You Jerk!. Mandark is always trying to kiss Dee Dee on the lips which is seen in episodes such as Momdark and Babe Sitter and in the episode Used Ink he actually did.
- Lee Lee & Mee Mee - Lee Lee & Mee Mee are Dee Dee's two best friends in the series. Their two young girls that share her intrests, personality, fashion sense, and even name sounds. Dee Dee, Lee Lee, and Mee Mee are almost just like each other. They always spend their times just being girls and having fun. The three of them all go to the same ballet classes together where they are the three best students with Dee Dee being the best, Mee Mee being the second best, and Lee Lee being the worst.
- Mom and Dad - Dee Dee's parents have never had problems with Dee Dee. She is almost never seen in trouble with either of them because she is such a nice little girl who always obeys what they say.
- Koosalagoopagoop - Koosy is Dee Dee's imaginary friend who she is playing with sometimes in the imaginary world of Koosland. they go on crazy adventures in there and love to play games and have fun. Dee Dee is the only one who can see Koosy because she is the only one who believes in him. He is completely invisible to others unless she makes them believe which she did to Dexter.
- Lalavava is Dee Dee's worst enemy. The way she and her act toward each other is just about a mirrored relationship to that of Dexter and Mandark's.
- Oceanbird once hired Dee Dee to babysit Mandark. She likes her and thinks of her as a friend to the family despite her rivalry with Lalavava.
- Monkey - Whenever Monkey is not in his secret supehero form, he pretends to be a normal old trained lab monkey. Dee Dee is sometimes playing with Monkey and dressing him up in girly costumes and having tea parties with him despite him being a male monkey. Monkey doesn't seem to be bothered by this because he must enjoy doing it being his only time not doing work and fighting evil and actually just goofing off anf having fun aside from his dates with Agent Honeydew. Dexter always seems to only want to do work and tests with him being a reason he likes Dee Dee's games alot better.
- Beau - Beau is Dee Dee's love intrest and boyfriend. He was first seen in the episode Beau Tie.
Role in creation of Koosland
Dee Dee's imagination had been creating philanthropic imaginary friends since she was a baby. The most known of her characters is Koosy, his full name being Koosalagoopagoop. An interesting thing is that even though these characters are "imaginary" and thus not existent in the reality, Koosy seems able to teleport himself from Dee Dee's mind into the material reality, also interacting with material things in a natural way. The place where Koosalagoopagoop lives is called Koosland or Planet Kooz. It is an imaginary world of happiness, beauty and cute, harmless creatures. The happiness is almost never disturbed, with an exception being the Jeepers, Creepers, Where is Peepers? short, when the evil character Hokochoo tries to destroy Planet Kooz. Peepers is the first creation of Dee Dee's mind, the first character in Koosland. It is told that he gave away so much happiness for all the creatures in Koosland that there was no more left for himself.
Cartoon Network: Punch Time Explosion
She appears in the game as an assist character and is a Synergy partner with Flapjack in the Console version. In the Dexter's Lab boos fight. Aku is the one who is being fought with and she keeps on playing with him when he changes into an animal, holding him still so that other players can easily attack him.
- "Hi Dexter!" - Various Episodes
- "Ooooooh! What does this button do?" - Various Episodes
- "I'm just here to check up on my favorite little brother, Dexter" - Changes
- "Oh Dexter, Dexter come quick! You sent me, and me!" - Dee-Dee-Dee-Mensional
- "But I want to push the button." - Dexter's Assistant
- "Your club is for big I D K S C's" - Decode of Honor
- Don't be silly! I love you very much! - LaBretto
- Oops! I guess I shouldn't touch! - LaBretto
- "Play with you Dolly Susie" - Babe Sitter
- "Fine! I don't need your stinkin' lab, i've got my own stinkin' lab!" - Dee Dee's Lab
- "I'm not rude you are!" - Rude Removal
- "Oh Yeah! You're the rude one brother!" - Rude Removal
- "Me?! I'm not the one who built that stupid thing!" - Rude Removal
- "Hello, dear brother! What have you got there? - Rude Removal
- Dee Dee is practically the opposite of Dexter.
- While Dexter loves to create, Dee Dee loves to destroy.
- While Dexter is mature and intelligent, Dee Dee is childish and ditzy.
- While Dexter is always busy and is used to working, Dee Dee is always free and spends her time playing.
- While Dexter is short and has very small legs, Dee Dee is tall and has very long legs.
- While Dexter is very annoyed by Dee Dee and somewhat hateful to her, Dee Dee loves to spend time with Dexter and deeply cares for him.
- While Dexter's favorite color is blue, Stupid Sister's favorite color is pink.
- While Dexter is a boy, Dee-Dee is a girl.
- Dee Dee is not smart and Dexter is smart
- Dee Dee shares many similarities with Harley Quinn, with their clueless personalities and hairstyle that are similar to each others.
- Dee Dee's favorite color is pink.
- Dee Dee's birthday was never mentioned, however she mentions she's a Cancer.
- Her feet are very large, this is addressed throughout the series, and in the episode "Shoo Shoe Gnomes" she is seen to have high-rampant foot odor.
- A running gag in the series is Dee Dee showing Dexter her "new" dance called "the Fanciful Unicorn" over and over again, forgetting she has already showed him many times.
- Dee Dee has two friends named Lee Lee & Mee Mee who both look like her and have similar sounding names.
- She has been called a "golden haired angel" by both Mandark and Nice Dexter.
- Dee Dee has a rivaly with Lalavava the same way Dexter does with Mandark. Ironically, they are both their sisters.