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Voiced by: Christine Cavanaugh (First two seasons, Ego Trip, and first five episodes of Season 3), Candi Milo (Remainder of Season 3 and Season 4), Jeff Bennett (his Future Badass self in Ego Trip and his superhero self in "Comic Relief")
- AcCENT Upon the Wrong SylLABle: "Dee-DEE, get out of my laBORatory!"
- The Ace: When it comes to science, of course. There was even an episode where one of his teachers clearly has the hots for him.
- Adorably Precocious Child: Taken Up to 11 in fan-works.
- Adorkable: Oh yes. He's a very brainy child whose awkward and shy personality is loved by the fans.
- Always Someone Better: Proves to be this to Mandark, especially by end of the latter's first appearance. Best shown in "Mandarker" where the two compete in a science fair. Mandark is an inconsolable mess still hung up on his destroyed lab and has to resort to supernatural methods because he can't come up with anything on his own while Dexter effortlessly impresses the judges with one of his "scribbles" and has moved on from being forced to shut down his lab.
- Ambiguous Disorder: Despite being a genius, he has No Social Skills and has trouble understanding basic concepts; for example, in different episodes, he has no idea what flour and chicken pox are.
- Animals Hate Him: As seen in an episode when Dee-Dee tries to get him to play outside numerous times and animals constantly beat him up. At the end of the episode, when Dexter is finally able to relax outside, several animals, including a fish, jump out of nowhere onto Dexter in a Big Ball of Violence.
- Aside Glance: Has done these on occasions whenever he's annoyed by someone (usually Dee-Dee).
- Badass Beard and Bald of Awesome: One of his future selves in Ego Trip is very muscular, has a beard, and is bald.
- Badass Bookworm: He is a tiny, stub-limbed boy genius who spends all his time in his secret laboratory, trying — in vain — to keep his pretty-princess Cloudcuckoolander sister out. Until a monster attacks the city, or aliens invade, or a meteor threatens Earth; then Dexter pulls out one of his giant, anime-inspired robots, super-powered exoskeleton suits, or space ships and kicks ass. He also seems to have learned kung-fu at some point.
- Berserk Button: Do not enter his lab.
- Big Brother Instinct: Or little brother, in this case. Mess with his sister, and you're dead meat.
- Big Good: In "Ego Trip". Also in any crossovers with other Cartoon Network franchises, he's either this or the de facto Leader including Cartoon Cartoon Fridays and FusionFall.
- Big "NO!": He gives these out frequently when something bad happens to him or Dee Dee ruins something.
- Butt-Monkey: Nothing goes right for this kid. Nothing.
- Cain and Abel: Usually the prickly Abel to Dee Dee's oblivious Cain, but Dexter falls squarely into the former category when he and his future selves create a quintet of mechanized assassins to kill his sister as punishment for saving human civilization when he was just inches away from doing so himself.
- Catch-Phrase: "Dee Dee get out of my lab-OR-a-tory!"
- The Chew Toy: He suffers this greatly in alot of crazy forms. For example, his entire lab is completely destroyed, the earth is destroyed, Dexter is turned into a sandwich, etc. He also gets into big trouble from his mom and dad as well. Especially his backbone-lacking teenage/young adult self in "Ego Trip", who works for Mandark designing cubicles in the future.
- Child Prodigy: A self-described "boy genius" with his own hidden lab.
- Clock King: Dexter once bought an expensive popsicle and paid with pennies. When the ice cream man asked Dexter how long it took him to count the pennies, Dexter correctly answered the question.
- Create Your Own Villain: Dexter unintentionally did this to Mandark when he laughed at the latter's Embarrassing First Name, which happened to be "Susan."
- Crouching Moron, Hidden Badass: Of a sort. Dexter tends to fail spectacularly at any form of physical activity, particularly sports... until the backdrop changes from "sports" to "Deedee let a giant monster out of the wormhole machine." Basically, he's an exaggerated stereotype of nerds are wimps up until science is involved. He can also go from deflecting lasers with his wrench like a Jedi to slap-fighting his rival and somehow manages to be in character both times. Rule of Funny is involved, but still.
- Deadpan Snarker: Especially in his interactions with Dee Dee.
- Depending on the Writer: How smart he is can differ from episode to episode.
- Didn't Think This Through: Tends not to consider the full ramifications of his inventions and schemes.
- In "Morning Stretch", he used a time-slowing helmet to turn thirty seconds into thirty minutes, allowing him the time to get ready for school. He failed to realize that the slowed time would prevent him from properly taking a shower or making breakfast, and his homework ignited from Friction Burn when he tried to finish it.
- In "The Continuum of Cartoon Fools", he gets so desperate to keep Dee Dee out of his laboratory for good that he destroys all the secret entrances and locks the front door, realizing too late that this would keep even himself from entering the lab.
- In "Comic Stripper," when he realizes that Mandark is getting his latest Evil Plans from the comic book Mister Misery, he buys every copy of the next book in an effort to beat Mandark at his own game, expecting him to do the same. However, Dexter is caught unprepared when Mandark instead copies the comic book Dangerous Duck. It didn't occur to Dexter that since he bought all of the copies of Mister Misery, Mandark wouldn't be able to get the new issue and copy Mister Misery's moves; Mandark even lampshades it.
- Ditzy Genius: He's able to time-travel, create robots and build portals to other dimensions, but is utterly incapable of taking care of himself for a single day when his mom is sick. He doesn't know how to cook (having never heard of "flour"), and as for cleaning... Also why would he put buttons and triggers in places Dee-Dee would obviously activates. In general, what he has in scientific smarts, he lacks in common sense.
- Earn Your Happy Ending: It takes a lot of hardship and more than a few decades, but Dexter's genius eventually makes the world a better (and smarter) place as Ego Trip shows.
- Emperor Scientist: He grows up to be an incredibly benevolent, if scatterbrained, elderly inventor who presides over a sublime Utopia.
- Enraged by Idiocy: Is easily angered by Dee-Dee's ditzy behavior.
- Extreme Doormat: His early 20's self in Ego Trip is this to Mandark.
- Eye Glasses: The glasses can change shape depending on expression.
- Fatal Flaw: Dexter has three that are almost always his downfall:
- His temper. Dexter proves able to handle Dee Dee effortlessly when he takes a moment to think but he has a Hair-Trigger Temper that makes him default to impulsive action when it gets set off.
- His pride. Dexter has a very high opinion of himself, disproportionate to his actual competence, which has caused him some major issues. Dee Dee can manipulate him into doing things by implying he isn't as smart as he holds himself to be and if he believes that someone is his superior in ways to deems meaningful then it tends to break Dexter. Badly.
- His devotion to science. He will sometimes employ convoluted scientific methods to achieve his goals, often overlooking more simple solutions that would be unlikely to blow up in his face.
- Fiery Redhead: His family is split evenly between this and the Dumb Blonde stereotype; he and his mother are fiery redheads and his sister and dad are happy-go-lucky yellow-haired ditzes.
- Foolish Sibling, Responsible Sibling: The Responsible to Dee Dee's Foolish.
- For Science!: His Catch-Phrase.
- Future Badass: Invoked in the Made-for-TV Movie, Ego Trip, wherein Dexter travels to the future for the primary purpose of seeing what kind of badass he is. In the dystopian future version of himself, he comes to resemble his hero Action Hank: big, brawny, and bearded (and unlike Hank, he goes bald), and his Mad Scientist pseudo-Germanic accent is replaced by an Arnold impression.
- Future Loser: This trope is also averted in Dexter's other two future versions, a wimpy office drone and a hilarious old man. The Future Badass version of Dexter exists between the two chronologically. However, we eventually see the former take a level in badass.
- Gadgeteer Genius: Dexter created a lot of stuff in the series.
- Good Is Not Nice: He's an egotistical jerk, but undeniably a good person.
- Grade Skipper: Dexter once went to college. At first, all other students only wanted to party and he refused to join, despite their warnings about getting it out of the system. By the time Dexter proved them right by buckling under the strain, they were the ones who only wanted to study for the upcoming finals. His attempt to make a wild college party happen anyway got him expelled. In another episode, Dexter was considered for grade-skipping but needed to improve his P.E. grades. He cheated his way into victory and ended up becoming Dee Dee's yearmate.
- Height Angst: In "Ewww, That's Growth", Dexter and his family want to go on a really big rollercoaster, but Dexter is denied due to being too short. The resulting angst drives him to become as tall as possible, eventually allowing him to finally go on the rollercoaster by the end of the episode. This backfires when he becomes so tall that he hits the ceiling at the very end.
- Herr Doktor: Dexter is a Mad Scientist with a German accent — made more blatant (and funny) since none of his family has any accent or gives any indication they have any German ancestry
- Hoist by His Own Petard: He sometimes suffers when his inventions malfunction at the wrong time, or work against him because he didn't think things through.
- Identical Grandson: He's a younger version of his grandfather.
- Idiot Hero: He can time travel and build an underground lab miles long but will go through hell and back to buy ice cream that he could easily make at home.
- Improbable Weapon User: He's pretty handy with a wrench in matters of melee combat as well as mechanics.
- Innocent Prodigy: In one episode he sees a repair-man working on the house's electrical system, and after some failed attempts to find out what he's up to using technology, Dexter's Plan C turns out to be to run off to "mommy" and ask her who's the strange man messing around with the fuse box. In another, he treats a burnt out light bulb as a kid would the death of a beloved pet.
- Insufferable Genius: He can be very arrogant when it comes to his smarts.
- Jerk with a Heart of Gold: He's not a bad person, but he can be quite rude, condescending, and egotistical.
- Large Ham: He can be quite expressive and loud, especially when he yells at his sister to get out of his laboratory or is gloating about his latest scientific achievement.
- Like Parent, Like Child: He's a Fiery Redhead like his mother. She is also the source of his boundless pride and creative impulses.
- Machine Worship: It's implied at many times that Dexter actually has a reverence for technology and science on a religious level. During Ego Trip, the Dexters from various time points all prayed to a deactivated Computer before getting to work and Dexter had once referred to notable past scientists in as "Disciples of Science" in Star Spangled Sidekicks. Not to mention his personal relationship with his Computer which he referred to as "his one true love".
- Mad Scientist: Not villainous example, obviously. The premise of the show is that Dexter is a kid mad scientist with a secret laboratory.
- Manchild: Teenager Dexter from "Babysitter Blues" and Old Dexter from "Old Man Dexter" could be excused on the grounds that both circumstances had Dexter accelerate his age to woo his sitter and watch the late night movie with his family respectively, but Future Badass Dexter cements it by whining he should've been the one to save the future and goes on with the plan of creating robots to destroy Dee Dee.
- Naked People Are Funny: Frequently seen nude, be it in the shower or by complete accident.
- The Napoleon: He has the short stature and the attitude.
- Narcissist: He has a very high opinion of himself. Case in point: in "The Parrot Trap," he built a robotic parrot purely so he could hear it repeat his own self-indulgent praises. The entirety of Ego Trip happened because Dexter couldn't fathom the idea that he didn't save the world, Dee Dee did.
- Nerd Action Hero: He has his moments in the show, being a super scientist with an assortment of cool robots and gadgets, but it really becomes true for his Future Badass version seen in Ego Trip.
- Nerd Glasses: He has thick framed glasses that double as Eye Glasses.
- Nerds Love Tough Schoolwork: Looks forward to hard tests.
- No Respect Guy: He's Surrounded by Idiots and hardly gets any respect.
- Not So Above It All: Dexter often participates in the foolishness of not only Dee-Dee, but the other kids his age. Justified, considering that despite him being more intelligent than his ppers, he is still a child.
- Omnidisciplinary Scientist: It may be easier to look for what areas of science Dexter HASN'T covered throughout the show.
- Ping-Pong Naïveté: He had his moments of stupidity. One example is when he thought he was going to die...because he had gas. We're talking about a boy genius that has done everything from go inside his sister's body to traveling to other planets using his inventions. To "simulate" the gas buildup in his lab, he used a balloon to represent himself. In other episodes/shorts, he didn't know what the "strange protrusions" all over his body were (he had the chicken pox) and tried to do a search through the entire animal kingdom for the "species" known as... the girl.
- Plot-Sensitive Snooping Skills: Despite all the tests he put Monkey through after giving him super powers, he failed to notice any changes.
- Precocious Crush: On Lisa, the babysitter.
- Ridiculously Successful Future Self: His future self is the ruler of a utopia.
- Savvy Guy, Energetic Girl: Savvy Guy to Dee Dee's Energetic Girl.
- Science Hero: He is a Child Prodigy who owns a huge underground laboratory.
- Sensitive Guy and Manly Man: Sensitive Guy to his Father's Manly Man.
- Shorter Means Smarter: Not so much when paired with his much taller rival Mandark, but definitely when paired with his taller sister Dee Dee.
- The Short Guy with Glasses: He's two feet tall.
- Small Name, Big Ego: Became one in later seasons due to Flanderization.
- Smart People Know Latin: Or take it, anyway. In "Accent You Hate" he's shown opening his locker and saying "Good morning" to his Latin and math textbooks.
- Swiss Cheese Security: No matter what measures he takes, Dee Dee always manages to slip into his laboratory without any trouble.
- Teacher's Pet: Although Mandark gives him some competition.
- Throw the Dog a Bone: Ego Trip, as the title implies, is basically an entire movie of Dexter finding out that all his efforts pay off...eventually.
- Took a Level in Badass: In "Ego Trip". Teenage Dexter is portrayed as a complete wuss. Until Madark breaks his glasses.
- TV Genius: He's a world renowned genius capable of building time machines, giant robots and create all sort of genetically modified creatures, yet thinks "girl" is some kind of tribe, doesn't know what dirt is, and one time thought he was going to die due to having gas.
- Unexplained Accent: Possibly a meta-Author Avatar related reason: Tartakovsky was born in the Soviet Union and moved to the United States as a child. He (most likely) has one as a child.
- The Unfavourite: His parents usually love him and his sister Dee Dee equally, but one notable instance of this trope is in "Oh, Brother", where Dexter turning his sister Dee Dee into a brother named Doo Dee resulted in Doo Dee getting all the attention while Mom and Dad ignored Dexter.
- What the Hell Is That Accent?: Dexter has a very peculiar accent that is either aiming for a stereotypical Eastern European accent, or a Bulgarian accent. Even Genndy Tartakovsky isn't certain what his accent is supposed to be.
- World-Healing Wave: The purpose of the Neurotomic Protocore is to send out such a phenomenon which would boost the joint intellect of mankind to superhuman levels, eliminating ignorance and promoting universal peace & brotherhood. It can also do the exact opposite, sucking in the intelligence of human beings worldwide to solely enrich the mind of its user, which is why Mandark wanted it so bad. However, while Dexter was able to create the core itself when he was just a child, it would be decades until he or Mandark would find a way to actually tap into its power.
Voiced by: Alison Moore (Season 1 & 3), Kathryn Cressida (Season 2 & 4), Kevin Michael Richardson (deepened voice in "Dee Dee Be Deep"), Pamela Adlon (gender-bent self Doo Dee in "Oh, Brother")
- Accidental Hero: At the end of Ego Trip when she pressed the button that reversed the effects of the neurotomic protocore that Mandark used to make everyone idiots, much to the ire of the Dexters.
- Action Girl: When the situation calls for it.
- All Girls Like Ponies: She is a pony fancier, as are her cloney best friends. There was the episode where she asked Dexter to turn her into a pony because she liked the My Little Pony expy so much.
- Ambiguous Disorder: Sometimes has hints of this - she lacks a lot of social intuition, can't take a hint, seems to be very temperamental, and even her own friends get frustrated by her odd behavior at times.
- Annoying Laugh: It sounds like a horse's neighing, only high-pitched.
- Annoying Younger Sibling: Actually an "Annoying Older Sibling" to Dexter, constantly breaking his stuff among other things.
- The Bad Guy Wins: There are several episodes that end with her getting her way and Dexter suffering in someway, usually with his lab being wrecked or completely destroyed by her. To list a few examples:
- In "Dexter's Assistant" she becomes a genius that's smarter than Dexter, and after she quits being his assistant she wins the science fair he enters.
- In "Game Over" she successfully defeats Master Computer and saves Dexter and his lab. But instead of getting him out of his computer she inserts a new game and starts beating him up, on the grounds he can no longer get mad if she beats him at games.
- In "Monstory" she and Dexter both become monsters and she tries to tell him a long and annoying story. They eventually fight and Dee Dee wins, pinning Dexter down so she can finish and force him to listen. It turns out her story was just a long knock knock joke, which she said early it wasn't.
- "Trick Or Treehouse" has her trap Dexter in her treehouse after he spent the whole episode wondering what she was doing in a tree. Since he broke into her treehouse she decides to go have fun in his lab and the episode ends with the sounds of her destroying Dexter's lab as he begs her to come back.
- Berserk Button:
- When Dexter wouldn't listen to her long-winded story about her day, she burst into tears, turned into a giant monster and went on a rampage.
- She gets furious when Dexter uses one of her dolls as an experiment.
- Beware the Nice Ones: Dee Dee is quite a force to be reckoned with if angered.
- Beware the Silly Ones: God help you if you make Dee Dee seriously angry.
- Big Sister Bully: Her treatment of Dexter has shades of this at times. In one episode, she stole Dexter's money right out of his hands to buy something, and when Dexter asks why she did so, she tells him point-blank, "You're so small and weak that I could!"
- Big Sister Instinct: Mess with her brother, and you're dead meat.
- CloudcuckooLander: She is born in Cuckooland. It is especially evident when she tells Dexter her bedtime story while she's sick, mixing a variety of common childhood nursery rhymes and stories.
- Crouching Moron, Hidden Badass: While Dee Dee is very ditsy, she's actually capable of taking on serious threats that Dexter is too weak to fight without his inventions.
- The Cuckoolander Was Right: In "Chicken Scratch", she is shown to be right about scratching chicken pox causing one to turn into an evil contaminated chicken.
- The Cutie: A bubbly, ditzy, lovable little girl who wears pink.
- Deadpan Snarker: When she's not being a ditz, tends to snark.
- Depending on the Writer:
- Gets hit with this pretty bad. How nice or annoying she is varies wildly from episode to episode. In some episodes, she's rather innocent and her destructive tendencies are accidental and due to playful clumsiness. In others, she's far more malicious and intentionally antagonistic.
- She flip-flops from stupid to a Straight Man for Dexter.
- The Ditz: The trope namer for "What Does This Button Do?". She often annoys Dexter because of her idiocy.
- Does Not Like Shoes: She spent nearly the entirety of "Sassy Come Home" proudly running around barefoot after she took off her "goshforsaken boots", which attracted a new playmate- Sasquatch.
- Slightly related- she got frustrated by a bunch of shoe gnomes who all tried to immortalize her feet when she bared them in the act of trying on their shoes.
- She also stomped an oversized amount of laundry into a washing machine shoeless.
- Dreadful Musician: She has an absolutely terrible singing voice. Doesn't stop her, though.
- Dumb Blonde: A mix of this and CloudcuckooLander...though she has her moments.
- Dumb Is Good: Much more cheerful and pleasant than Dexter.
- Early Installment Character-Design Difference: Had thick eyebrows and seemed to lack a chin in early episodes.
- Foolish Sibling, Responsible Sibling: The Foolish to Dexter's Responsible.
- Genius Ditz:
- She gives a somewhat accurate description of Gregor Mendel in the Sasquatch episode. She can break through any security measure Dexter comes up with. When she's not wrecking them, can use Dexter's inventions with instant mastery, like a hovercraft Dexter himself crashed or an incredibly complicated giant mech.
- A subtle moment from the show's opening titles implies that Dee Dee is smarter than she lets on: Dexter frantically presses a button, attempting to turn on a large light, then Dee Dee briefly gives Dexter an aside glance and coy smile and plugs a cord into a nearby socket, successfully turning on the light.
- Genki Girl: She's an extremely energetic, hyperactive girl.
- Girlish Pigtails: Blonde pigtails.
- Girls Love Stuffed Animals: She loves her dolls.
- Girly Girl with a Tomboy Streak: Sure, she likes playing with dolls and ballet, but she also likes video games, sports and rollerskating.
- Hair of Gold, Heart of Gold: A blonde girl who loves her little brother to no end.
- Hypocritical Humor: Whenever Dee Dee meets someone of her own clingy and destructive level, she finds them intolerable and inconsiderate. For example, in the pilot episode, when she finds out that Dexter broke into her room to steal one of her dolls for experiments, she completely loses it and confronts him, while ignoring the fact that she regularly breaks into his lab uninvited and destroys it without a care for Dexter's feelings. Then we have Dollhouse Drama, in which she steals one of his miniatures, brings it back to her room, and plays with it.
- Idiot Houdini: Dee Dee always made a huge mess of Dexter's lab through her sheer idiocy, sometimes even causing quite a lot of destruction among others as well, yet she almost never got any repercussion for it. Seasons 3 and 4 were a little better about averting this. Partly because there were fewer episodes that had Dee Dee in the lab but she was a lot more prone to actually getting called out for her antics. It helps that there were times that she actually did try to clean up the messes she made and that she either went down with Dexter or suffered as a result of her own actions.
- Innocent Blue Eyes: She has blue eyes and is definitely naive.
- Innocently Insensitive: Dee Dee is usually just a playful Genki Girl who wants to play with her little brother. However her notions of fun include playing around with his pretty looking (and somewhat delicate) toys, and no amount of ranting at her to leave him alone ever seems to faze her.
- Jerkass Ball: Oh, boy. She holds several of these moments where she acts more downright malicious than Innocently Insensitive.
- Karma Houdini Warranty: There are episodes where she gets her comeuppance.
- Kiddie Kid: Dee Dee is elder to her titular brother, and the "Picture Day" episode implies that she is in the sixth grade. This would put Dee Dee's actual age somewhere between ten and twelve, but she tends to behave as if she were younger than Dexter.
- Knight Templar Big Sister: Dee Dee may appear to be a flake, but you do NOT harm her little brother. Or she will kick your ass.
- Leitmotif: This whimsical, piano piece that plays when she shows up, usually when dancing.note
- Lethally Stupid: She usually sabotages Dexter's experiments and destroys his lab, although she does so out of ignorant curiosity rather than malicious intent.
- Like Parent, Like Child: Her dad is where she gets her lack of foresight and curiosity.
- Lying Finger Cross: In comic book story "Salt and Pepper", Dexter and Dee Dee make a deal where she'll stay away from his lab forever. When he tries to collect, she reveals that she crossed her fingers.
- Motor Mouth: She quite often speaks very rapidly, just barely able to be coherent without speaking slowly.
- Nice Girl: She's pretty darn sweet and she absolutely adores her little brother. Her destructive tendencies are usually due to clumsiness or carelessness rather than malice, and sometimes it's shown that the reason she's always sneaking into Dexter's laboratory is because she just wants to spend time with her brother.
- No Indoor Voice: She frequently yells at the top of her lungs.
- No Sense of Personal Space: Pretty much the defining premise of Dee Dee's character. It's rare for her to leave her brother alone.
- Oblivious to Love: Mandark is in love with her but she seems unaware of it.
- Only Known by Their Nickname: Even her parents call her Dee-Dee. It's more a case of One Mario Limit since "Dee Dee" is an actual name.
- Our Mermaids Are Different: Dee Dee pretended to be a Mermaid swimming in the sea in "Ocean Commotion" episode.
- Person of Mass Destruction: Every time Dee Dee manages to get into Dexter's lab, she almost always leaves a massive amount of destroyed machinery and inventions in her wake. In Mandark's debut episode, Dexter even used this to his advantage to get back at Mandark.
- Pet the Dog: She may constantly be wrecking Dexter's stuff and annoying him to no end, but it is shown on more than one occasion that she actually does care about her younger brother.
- Pink Means Feminine: Along with her two friends, who wear the same clothes as her.
- Repetitive Name: Dee Dee.
- Savvy Guy, Energetic Girl: Energetic Girl to Dexter's Savvy Guy.
- Spanner in the Works: Especially in Ego Trip, when she wanders through the time portal at the end of the movie, goes "Oooh, what does this button do?", then pushes it and leaves.
- Sweet Tooth: She loves candy.
- Unsportsmanlike Gloating: Whenever she beats Dexter in a game, she will always taunt him for it. In "Game Over", for example, every time Dee Dee beats Dexter at video games, she relentlessly rubs it in his face, dancing around the room and chanting "I won!". And when Dexter tells her he doesn't want to play with her anymore, she calls him a Sore Loser.
- Walking Disaster Area: At least whenever she's in Dexter or Mandark's lab. Or being abducted by aliens. Otherwise she manages to keep the property damage to a minimum.
- What Does This Button Do?: The Trope Namer. Dee Dee elevated this to an art form, as this would usually be the last thing Dexter would hear before one of his inventions goes awry. She sort of Lampshaded it in the episode where Dexter's trying to sleep:Dee Dee: I went into your lab... and, I pushed this button...
Dexter: Oh, just like the last thousand times?
Dee Dee: I think it's really serious this time... (cut to self-destruct device counting down)
Voiced by: Jeff Bennett
- Abusive Parents: Downplayed, as he isn't horribly abusive, but as shown in several episodes, such as "Better off Wet," Dexter's dad can be a bully, embarrassing and pulling childish pranks on his family for his own enjoyment. These often include pushing his family in the pool, and very manipulative behavior.
- Amazingly Embarrassing Parent: Has a tendency to humiliate his kids on accident.
- Art Evolution: His appearance after the reboot had him a lot skinnier.
- Berserk Button: You can threaten him, you can break his car and he'll just brush it off. But don't ever not-hold a door open for a lady—ESPECIALLY his wife!
- Beware the Nice Ones: Hoo boy - there's his Manipulative Bastard tendancies, for a start. Then there's the times he gets really mad...
- Bumbling Dad: Both parents are bumbling, though their primary flaw was being clueless to Dexter's Laboratory (and he has a memory erasing gun, so its more like they look stupid by comparison to their supergenius son.) Dexter's father turns out to be a stunt biker when his job is finally revealed (up to then, he left every day dressed for an office job), making him much cooler and more competent than the typical example.
- Crouching Moron, Hidden Badass: And when it happens, watch out.
- Dumb Blonde: Subverted - while he's clearly not as smart as Dexter, he possesses average intelligence, and has moments of genius.
- Enfant Terrible: When Dexter turned him into a baby, Dad took a lot of enjoyment out of hurting his wife (also turned into a baby) with Dexter's machines.
- Eye Glasses: Like Dexter's glasses, they can change shape depending on expression.
- Flanderization: Became a Small Name, Big Ego in the later episodes
- Genius Ditz: He's generally pretty care free and goofy, but he can be surprisingly crafty and manipulative when he wants to, bordering on The Chessmaster. If mom's muffins are involved, watch out!
- Happily Married: To Dexter's Mom.
- Jerk with a Heart of Gold: While he tends to pull petty pranks on his family, he does care for them.
- Jock Dad, Nerd Son: He's the Jock Dad to Dexter's Nerd Son.
- Manchild: As seen above, he can be very childish and immature.
- Manipulative Bastard: He's this when he wants to be in "The Muffin King" and "Snowdown".
- No Name Given: His first name is unknown.
- Papa Wolf: He'll go through all sorts of danger if his kids are in trouble.
- Parental Obliviousness: It's amazing how he, along with Mom haven't figured out that the lab exists.
- Sanity Slippage: In "The Muffin King", he gets so upset over his children preventing him from eating one of Mom's muffins too early that he ends up having a fantasy about ruling over a land inhabited by sentient muffins.
- Standard '50s Father: He walks a fine line between this and the Bumbling Dad.
- Took a Level in Badass: Dexter's dad goes from average middle class guy and sports enthusiast to daredevil stuntman in one episode of the later seasons.
- Took a Level in Dumbass: By the fourth season, he's become a complete nitwit. For instance, he doesn't know that he is being threatened legal action for stealing cable in "Bad Cable Manners" in spite of being repeatedly told so by the authorities that warn him and in "Tee Party" is shown to have no idea how golf works even though he was shown to be a fan of the sport in "Dad is Disturbed".
- Unnamed Parent: He is only called Dad.
- Would Hit a Girl: After being transformed into a baby, he had no qualms with injuring his wife with Dexter's inventions.
- Action Mom: Demonstrated in "Mom and Jerry", "World's Greatest Mom" and "A Mom Cartoon".
- Amazingly Embarrassing Parent: Most notably in the episode "Chess Mom", where she embarrasses her son while trying to cheer him on at the chess tournament.
- Ambiguous Disorder: Her obsession with cleanliness goes beyond what is healthy.
- Berserk Button:
- As seen in "Dexter's Rude Removal", the most Mom ever got beyond angry was when the rude clones of Dexter and Deedee not only made a huge mess of her kitchen during a food fight but used profanity as well.
- Germs, period.
- Beware the Nice Ones: Whenever her Berserk Button is pushed, or her children are threatened.
- Cute Bruiser: Dexter's mother has shown to be able to fight very well.
- Fiery Redhead: The family is split evenly between this and the Dumb Blonde stereotype; Dexter and his mother are fiery redheads, his sister and dad are happy-go-lucky yellow-haired ditzes.
- Flanderization: Her Neat Freak tendencies get played up considerably in the later episodes.
- Genius Ditz: Similarly to Dexter's dad. She shows frightening proficiency with technology when it comes to battling germs.
- Happily Married: To Dexter's Dad.
- Hartman Hips: The page image. In fact, when Dee Dee gets turned into a duplicate of Mom in one episode, she feels her hips with awe.
- Housewife: She seemed to have little characterization outside of her housework, though it's been implied a few times that she was a lot more rebellious in her youth. Her typical outfit that she wore everywhere even included yellow rubber dishwashing gloves and an apron.
- Iconic Item: Her yellow rubber gloves. So much so that she feels naked without them.
- Male Gaze: Cameras don't hesitate to get as many shots from the back as they can. "Better Off Wet" in particular features her in a bikini.
- Mama Bear: Best shown in "Go, Dexter Family! Go!", where hearing her son cry for help motivates her into breaking free from her bonds and kicking the aliens' asses.
- Mistaken for Badass: She once "defeated" the reigning snowball champion (Dexter's dad) by playfully chucking a snowball at him. He's been convinced ever since that she has evil snowball powers, which she passed on to Dee-Dee.
- Neat Freak: The episode "Pslyghtly Psycho" suggests that she is actually germophobic, particularly when her gloves and slippers are removed and she finds herself afraid to even set foot on the carpet barefoot.
- No Name Given: Her first name is unknown, although her maiden name is probably "O'Reilly," as seen in one episode that features her brother.
- Parental Obliviousness: It's amazing how she, along with Dad haven't figured out that the lab exists.
- Redhead In Green: She wears a pale green blouse-shirt with a wide collar, white apron and dark green pants. Also her bikini is green.
- Skewed Priorities: She favors cleanliness over anything. One episode has her ignoring the fact Dexter had destroyed her entire house over the fact he was clean.
- Unnamed Parent: She is only called Mom.
Voiced by: Eddie Deezen
- Affably Evil: He usually uses his manners, and has some Villain Respect for Dexter.
- Always Someone Better: He was this to Dexter before Villain Decay kicked in.
- Amazingly Embarrassing Parents: Not only are they hippies, but they had the audacity to name him Susan, which eventually helped to push him into his evil tendencies.
- Arch-Enemy: Dexter's rival.
- Asian and Nerdy: He's half-Asian and a genius.
- Badass Bookworm: It should be expected as he's Dexter's Evil Counterpart.
- Badass Cape: Gets one in Ego Trip and the later seasons.
- Bad Boss: His young adult self in The Movie, who punishes one of his employees (Dexter) for almost being late by lashing him in front of the other workers. One abuse too many leads Dexter to snap, beating Mandark's ass down and becoming his Future Badass self.
- Bald of Evil: His future self from the time of Dexter's Future Badass self has no hair on his head and has taken over the world by using the neurotomic protocore to make everyone else dumb.
- Big Bad: His appearances weren't as frequent in the first two seasons, but he is unquestionably the main villain in Ego Trip and the final two seasons.
- Brain in a Jar: His ultimate fate at the end of "Ego Trip."
- Breakout Villain: Appeared infrequently in Seasons 1 and 2, became pretty much the 3rd main character by the time the show ended.
- Can't Catch Up: Ego Trip reveals that his vast intellect has a cap to it which is why he starts to steal Dexter's ideas when they get older and the reason he uses the Neurotomic Protocore to steal the intelligence from the rest of the human race to enhance his own. All that "fat" his Bad Future self has? That's all grey matter.
- Characterization Marches On: A brief gag implied he had telepathy is his first appearance, an ability that was never brought up again.
- Child Prodigy: A boy Genius like Dexter.
- Corrupt Corporate Executive: His youngest future self in Ego Trip, who eventually took control of the company he and Dexter worked for and started using its resources to advance his plans for world domination.
- Dark Is Evil: His lab in post-finale seasons. Also, of course, his nickname.
- "Darkness von Gothick" Name: His preferred, self-given alias.
- Depending on the Writer: He's either a villainous mastermind or just some kid Dexter's rivals with.
- Disproportionate Retribution: His hatred and obsession with ruining Dexter is later revealed to have stemmed from their first meeting, where Dexter laughed at his Embarrassing First Name. To punctuate this, Dexter doesn't even seem to recognise Mandark the second time they meet.
- Dude Looks Like a Lady: Dexter's first mistook Mandark for a girl due to his effeminate wardrobe and long hair as per the results of his parent's lifestyle. The fact his name was also "Susan" made the comparison to a lady all the more apparent.
- Embarrassing First Name: Retconned to Susan.
- Entitled Bastard: In his debut episode, he genuinely expects Dexter to help set him up on a date with Dee Dee, despite the fact that he had spent the entire episode one-upping Dexter and forced him to shut down his lab; Dexter only goes along with it because he realizes he can exploit Dee Dee's destructive tendencies to have Mandark's own lab shut down.
- Even Evil Has Standards: After a day posing as Dexter's mother, he is left so exasperated from spending a day in her shoes (and ceaselessly tending to every single trivial problem the other family members whine over) he aborts the plan, yelling the family are nothing more than selfish creeps.
- Evil Counterpart: To Dexter; Tall and composed to Dexter's short and insecure. His younger sister, Olga "Lalavava" Astronomov, is this to Dee Dee, a short and solemn Technician to Dee Dee's tall and joyful Performer; while Dee Dee unwittingly destroys Dexter's creations but truly loves her brother, Lalavava bullies Mandark mercilessly and displays little to no care for him. His parents also serve as not so evil counterparts to Dexter's, being a pair of 60's era hippies in contrast to Dexter's straight laced 50's inspired ones. His intentions towards science are also diametrically the opposite of Dexter's for while Dexter engages in science to improve mankind and the boundaries, Mandark wanted to use science as an extension of his own malevolent tendencies and take over the world.
- Evil Genius: His talents and competence are equal to Dexter's but it's implied in Ego Trip that he's not as imaginative as Dexter can be, which limits his genius.
- Evil Laugh: "HA haha! HA haha haha!" The fact that he cries, coughs and chews in the same way makes it border on being a Verbal Tic.
- Expository Hairstyle Change: He was once long-haired, then got his iconic bowl cut when he decided to reinvent himself into Mandark, and those two bangs in the middle are the result of using a cracked bowl as his template, which fittingly form a meaningful "M" for Mandark similar to the way Matt Groening hid his initials in Homer Simpson's design as an easter egg.
- Eye Glasses: Much like Dexter, his glasses change shape to match his emotions.
- Fat Bastard: In the third future of Ego Trip, he is extremely obese and has to have a hook and later a robot carry him around. The official Cartoon Network Website nicknamed him "Fat Cat Mandark" back in the days it was still featuring digital collectibles that you could buy and trade these items from obtaining credits from playing games and being active on the website.
- Flanderization: Became more and more like a stereotypical Evil Genius as time went on. He was just originally portrayed as Dexter's rival and at his most repugnant, just wanted his lab shut down. Suddenly it went from that to trying to take over the world. To a lesser extent, his crush on Dee-Dee.
- Freudian Excuse: His parents were people perpetually stuck in the 60's summer of love (i.e. hippies) and constantly stifled his scientific curiosity. He tried his best to go along with it, but one chance meeting with Dexter on the day he moved into the neighborhood ended with Dexter laughing in his face. Needless to say that was the straw that broke the camel's back. Played With. He was shown to have always been born with a negative disposition and his parents really didn't understand him though when they did realized they were denying some of his needs, they left their home and traveled around, eventually settling in Dexter's neighborhood.
- Gender-Blender Name: His real name is Susan. He's very ashamed of it, too.
- Harmless Villain: After Villain Decay.
- Hippie Parents: Turns out Mandark's parents are hippies, and his real name is Susan, because they wanted to give him a name that fit "beyond the confines of society" and one without "preconceived connotations" as befitting their highly liberal views.
- Hopeless Suitor: Is head-over-heels in love with Dee Dee, who is unaware... at best.
- Ink-Suit Actor: Bares more than a striking resemblance to his voice actor, Eddie Deezen.
- Insufferable Genius: His ego is comparable to Dexter's.
- Jerkass: He makes Dexter's life miserable simply because he believes he's better than him.
- Knight of Cerebus: His villainy is taken much more seriously in "Ego Trip", since it is shown in the future that he has taken over the world and made everyone stupid just because he didn't want to share his knowledge with anyone else. Because of this, the future is shown to be a complete Crapsack World.
- Lean and Mean: He's a skinny Evil Genius.
- Light Is Not Good: Mandark's lab before post-finale seasons.
- Mad Scientist: An evil boy mad scientist with Evil Laugh and all.
- Meaningful Name: His vaguely Russian last name creates a parallel with Dexter's Eastern European Accent, and his first name drives him to reject the New Age hippie lifestyle in favor of hard science. His Russian sounding last name Astromonov also serves as a shout out to the series creator being a Jew from Russia. It's implied his father may be of Russian and perhaps Jewish descent to parallel Genndy Tartakovsky while his Asian mom parallels Yoko Ono.
- Multiple-Choice Past: He has two different origin stories.
- Nerd Glasses: He wears thick framed Eye Glasses like Dexter.
- Not So Different: Both Dexter and Mandark are defined by their childish egos and temperament, to the point it's no surprise either would be completely insecure about the other's intellect and resent one another.
- Not-So-Harmless Villain: Ego Trip eventually proves he can still be a threat, even after his Villain Decay.
- Ominous Opera Cape: Wears a long black cape in his alternate getup.
- Only Known by Their Nickname: His real name is Susan.
- Pet the Dog: When he's actually siding with Dexter or just taking a break from evil in general.
- The Power of Hate: While he was always intellectually gifted, he boosted his scientific endeavours dramatically just for the purpose of one-upping Dexter.
- Red and Black and Evil All Over: His alternate getup is a costume colored red and black.
- The Rival: Dexter's nemesis and rival boy-Genius.
- Sissy Villain: In later episodes, his plans are more malicious, but his whiny nerdish persona remains in tact.
- Smug Snake: He's often portrayed as condescending towards Dexter.
- Teacher's Pet: Competing for the role with Dexter.
- Took a Level in Jerkass: In the revival seasons, Mandark becomes significantly more evil, becoming Dexter's enemy rather than his rival.
- Vague Age: It is difficult to tell if Mandark is actually elder to Dexter, or if he is the same age as him but just appears older. On one hand, Mandark is in the same class as Dexter, and is generally treated as his equal. On the other hand, Mandark has a younger sister, and Dexter is implied to be a Grade Skipper. Further confusing matters is Mandark's obsession with Dee Dee, who is older than Dexter and is suggested to be a sixth grader, which would make her a tweenager.
- Villain Decay: When Mandark was introduced first, he was portrayed as being much smarter than Dexter, and his lab was (and still is) even bigger and more impressive than Dexter's. However, after Dee Dee destroyed his lab, Mandark fell to second place, and is no longer Dexter's equal.
- Villainous Crossdresser: Once Mandark replaced Dexter's mom. No one in the family noticed it, until the real mom came by. Even then, they were completely stumped as to which was the real one.
- Villainous Crush: He has an unrequited crush on Dee Dee.
- Villain Respect: He hates Dexter, but respects him.
Mee Mee and Lee Lee
Voiced by: Kimberly Brooks (Mee Mee), Kath Soucie (Lee Lee)
- Asian Airhead: Lee Lee is Asian and she and Mee Mee are often depicted as being just as ditzy as their friend Dee Dee.
- Black Best Friend: Mee Mee is black and one of Dee Dee's friends.
- Chuck Cunningham Syndrome: Neither of them are anywhere to be seen in the third and fourth seasons.
- Pink Means Feminine: Both wear the same pink dress as Dee Dee.
- Spell My Name with an "S": In an early set of promotional training cards depicting scenes from the series, cards for their first appearance in "Double Trouble" spelled their names as "Li Li" and "Mimi." The credits for their second appearance in "Tribe Called Girl" spelled them the way their known today.
- Straight Man: Are occasionally shown as being more rational and intelligent than Dee Dee, if only by a smidgen.
- Theme Naming: Their names rhyme with Dee Dee.
- Those Two Girls: They usually appear together as foils to Dee Dee.
Voiced by: Dom De Luise
- All of the Other Reindeer: It is shown in the episode "Koosalagoopagoop" that everyone else in the Land of Koos dislikes him, though this changes at the end of the episode.
- Big Fun: He's a huge and obese creature and really loves to have fun.
- Blatant Lies: Whether he's downplaying his ability to change size or insisting he's king of Koosland, he's a bit of a chronic liar.
- Classy Cane: Briefly carries one when we first see him.
- Easily Forgiven: As far as any of his fellow imaginary beings are aware, he socked the king of Koosland in the face, took his crown, and kissed the queen. The king immediately forgives him for it.
- The Friend Nobody Likes: Dee Dee adores him, but Dexter's justifiably annoyed by him and he's resoundingly disliked in the Land of Koos. He makes a brief cameo in the Powerpuff Girls, where nobody likes him except Bubbles.
- Lethal Chef: He's exceedingly proud of his "Pepe wraps" — an industrial sized tub of meat slapped unseasoned onto a tortilla. And if you don't eat it willingly, he'll shove it down your throat.
- Nice Guy: He's very friendly and even attempts to get Dexter and the grumpy Peepers to lighten up.
- Nice Hat: He wears a little green hat.
- Signature Laugh: Has a distinctive, wheezy one that goes hand in hand with being voiced by Dom De Luise.
- Tulpa: He's Dee Dee's imaginary friend and has pretty much become a physical being ever since Dee Dee created him.
- Took a Level in Badass: In his first appearance he doesn't do much but bounce around, giggle, and make a nuisance of himself; in the second, he lies to Dee Dee to make himself look more impressive and likable and mostly gets dragged around by her. By the third, however, he's willing to steal Dexter's robot mecha to save Koosland — and, with Dexter, deliver a Shut Up, Hannibal! to the anime villain destroying it.
- Unexplained Recovery: His first appearance had Dexter imagine him away, supposedly gone forever in one hell of a Mood Whiplash Downer Ending. Obviously he would make recurring appearances afterwards, with no explanation how he was brought back, other than Dee Dee's perenially active imagination.
Lisa the Babysitter
- Hartman Hips: Due to the art style, lots of women in the series have Hartman Hips.
- Ms. Fanservice: She has a slender but curvy figure.
- Nice Girl: Lisa is shown to be very kind and friendly, and is evidently very good with children, seeing as she's a part-time babysitter.
- One-Shot Character: She only appears in a very early episode of the series and never shows up again after that. But look up any fanart of her and you'd be surprised at how much of it there is.
- What Happened to the Mouse?: It is unknown if Jeff and Lisa got back together after Dexter broke them up.
- Zettai Ryouiki: Wears thigh-high socks along with a navy-blue skirt.
Douglas E. Mordecai III
- First-Name Basis: The earlier seasons had Dexter refer to him as Douglas but after the show was brought back from cancellation Dexter started calling him Mordecai as if he always had been doing so.
- Hollywood Nerd: Douglas is a nerdy individual with geeky tendencies who shares much in common with Dexter.
- Nerd Glasses: Like Dexter, he has thick framed glasses that double as Eye Glasses.
- Satellite Character: He's Dexter's best friend. That's pretty much it.
Voiced by: Michael Armstrong ("Beard to be Feared"), John Garry ("Decode of Honor"), Kevin Michael Richardson ("911")
- Badass Beard: And in the episode in which he is introduced, he and Dexter (who had obtained his own beard through SCIENCE) join beards to fight criminals).
- Boisterous Bruiser: His strength is matched only by his good nature and noble intentions.
- Expy: Of G.I. Joe, Mr. T, and Shaft.
- Scary Black Man: A muscular black man and a crime fighter.
- Soul Brotha: He's an Affectionate Parody of the trope.
- Berserk Button: Children with "funny accents".
- The Bully: Towards kids with "funny accents".
- Defeat Means Friendship: After being beaten by the kids with "funny accents", he becomes friends with them.
- Heel–Face Turn: At the end of the episode.
- Politically Incorrect Villain: Has shades of this, given that his favorite targets were minorities.
Voiced by: Paul Williams
Mandark's Parents (Windbear and Oceanbird)
- Abusive Parents: While they're not the worst examples of the trope, they aren't very supportive of Mandark's love for science, and they gave him a name Susan that would subject him to a lot of ridicule from other kids. Mandark's father also is the first to actively attempt to shut down Mandark's scientific pursuits and displays anger problems when things don't go his way.
- Does Not Like Shoes: They always go barefoot, just like the utmost stereotypical hippies you can think of. Mandark did not take after them.
- Granola Girl: Oceanbird.
- Nature Lover: A couple of hippies connected to the earth who lived in a little woodsy village called Flowertopia with Mandark before moving to the city.
- No Celebrities Were Harmed: John Lennon and Yoko Ono, Windbear more so.
- Not So Different: Windbear at least ends up getting provoked into fighting Dexter's dad just like their sons do. Oceanbird is only implied, and even then it could end up the same as Dee Dee and Lalavava where they give up on it.
Yani The Janitor
- Almighty Janitor: A literal case.
- Freudian Excuse: Being abused by his wife.
- Gone Horribly Wrong: He ends up making a bigger mess in his attempt to get revenge on Dexter.
- Henpecked Husband: Part of his motive for trapping Dexter in the school is that he was abused by his wife.
- Jerkass Has a Point: While he did trap Dexter, Dexter did keep leaving a mess in the school laboratory, causing him to be overworked.
- Monster of the Week: Only appears in the episode "Trapped With A Vengeance".
Dial M for Monkey
- The Ace: Monkey In-Universe is the most powerful and respected hero on the planet.
- Action Pet: When off duty, his personality is similar to Dee Dee's and he is often seen playing with her in the laboratory, but when it is time to save the world Monkey is extremely serious and heroic and risks his very life to ensure the safety of the world and those he loves.
- Badass Adorable: Monkey is considered to be one of the Dexterverse top superheroes.
- Batman Can Breathe in Space: Apparently his energy field provides life support for himself and passengers.
- A Birthday, Not a Break: The banned "Barbequor" episode took place when the other heroes threw a birthday party for him, but even after he defeated the Barbequor and the Silver Spooner, Monkey wasn't able to enjoy his birthday because he then had to give Krunk a ride home and Krunk kept on giving very lousy directions on where his home was.
- Boxing Lessons for Superman: When Huntor's technology completely counteracts Monkey's powers, Monkey defeats the villain using only his skills, brains, and - uh - guerilla tactics.
- Determinator: In his fight with Rasslor, he kept on being knocked down, and wouldn't give up. Rasslor threw the fight (and decided not to destroy the Earth) because of this.
- A Dog Named "Dog": A monkey named Monkey.
- Everything's Better with Monkeys: He's a monkey and a superhero.
- Flying Brick: He can generate an energy field around his body that gives him this set of powers.
- Furry Reminder: Monkey is intelligent, but his instinctive reactions, body language and problem-solving skills are all quite simian.
- Heroic Spirit: He can be defeated (with humorous ease in some cases), but he'll never surrender.
- Interspecies Romance: He is often paired with his sidekick and girlfriend Agent Honeydew on his missions who he cares about deeply and appears to posses a psychic link with her.
- Kid-Appeal Character: In-Universe, Monkey is one of the most popular superheroes among children.
- Loves My Alter Ego: Non-romantic example. Dexter admires the super hero Monkey and has no idea that his lab monkey leads a double life. He remains thoroughly unimpressed that his monkey failed to developed super powers.
- Narrator All Along: "The Lab of Tomorrow" ends with the revelation that he was the one narrating the episode. No explanation is given for how he became capable of human speech.
- Out of Focus: His appearances became less frequent in the final two seasons. He did get a bizarre Day in the Limelight episode, though.
- Ridiculously Cute Critter: Monkey is cute both in and out of costume.
- Secret Identity: As Dexter's lab monkey. Dexter and his family are completely unaware of his double life.
- Suddenly Voiced: Is revealed to have become able to speak at the end of "The Lab of Tomorrow".
- Superhero: Considered the world's greatest superhero.
- Talking the Monster to Death: Convinces Simion, another super-simian, to abandon his plan of destroying the Earth in favor of swinging around in a jungle. Not bad for somebody who can only make monkey noises.
- Your Cheating Heart: Despite having Agent Honeydew as a girlfriend, "A Quackor Cartoon" shows him falling in love with Quackor, and in the later episode "Used Ink", one of the things that he asked for was a girl monkey implying that his relationship with Quackor might be over and he is looking for a new love. However in one of the final episodes of the series "Dexter's Wacky Races", Monkey is shown to be back together with Agent Honeydew. All of this was never explained.
- Action Girl: As part of her agent training, she is a trained fighter who is proficient in firearms.
- Boyish Short Hair: She has short black hair with curly bangs.
- Interspecies Romance: Despite their different species' (and the questionable ethics of this), it appears that Monkey and Honeydew's relationship is very close and romantic, as both are often seen going out on dates when off duty, sharing romantic dinners and Monkey staying over at her house where they apparently bathe together while she grooms him.
- Ms. Fanservice: She is a sexy spy.
- Raven Hair, Ivory Skin: Has pale skin and black hair.
- Spy Catsuit: She wears a violet-blue S.H.I.E.L.D.-style jumpsuit when is in mission.
Voiced by: Robert Ridgely (Season 1), Earl Boen (Season 2)
Voiced by: Brad Garrett
Quackor the Fowl/Ducky
Voiced by: Frank Welker
- A Dog Named "Dog": Her real name is Ducky.
- Dark Action Girl: After she's revealed to be female in her second appearance, we learn that she's this.
- Evil Counterpart: To Monkey. She is Mandark's pet duck and Monkey's arch-nemesis.
- Feathered Fiend: An evil duck.
- Heel–Face Turn: In her second appearance, due to falling in love with Monkey.
- Lunacy: She becomes Quackor when the moonlight hits her. Sunlight restores her to normal.
- Punny Name: Quackor the Fowl; "fowl" is a term for both ducks and chickens, while a homonym "foul" means "wicked" or "amoral".
- Rogues-Gallery Transplant: According to the The Powerpuff Girls episode "Bought and Scold", Quackor the Fowl is somehow one of their enemies.
- Samus Is a Girl: Implied in her second appearance; she and Monkey not only fall in love, but she lays an egg. So she's either a girl or a Mr Seahorse.
- Undying Loyalty: Implied to have this for Mandark in her debut episode, seeing as she goes off to destroy Dexter's lab after hearing Mandark mumble about wanting to do so in his sleep.
Simion the Monkey
Voiced by: Maurice LaMarche
- Everything Is Better With Monkeys: Simion is a chimpanzee.
- Humans Are the Real Monsters: He wanted to destroy humanity for the suffering their experiments on him brought him.
- One-Shot Character: He was never seen outside the episode: Simion.#
- No Celebrities Were Harmed: His voice was based on that of Charlton Heston's.
- Psychic Powers: Simion becomes enlightened and acquires the power of telekinesis and matter creation.
- Talking Animal: Unlike Monkey, Simion is quite eloquent.
- Tragic Villain: Wants revenge on humans for abandoning him.
Voiced by: Jim Cummings
Voiced by: Dee Dee Rescher
- Bald Women: She has no hair whatsoever. Honeydew lampshades the Irony of a hairless villain stealing other animals' fur to wear herself.
- Barbie Doll Anatomy: When stripped naked by Agent Honeydew, her exposed body is devoid of genitalia or any other detail.
- Cruella to Animals: She hires her goons Tanner and Skinner to kill animals just so she can have them made into exotic clothes.
- Cat Fight: With Honeydew, complete with hissing and noises. She's even wearing an outfit made of cat's hide at the time.
- Designated Girl Fight: Honeydew takes her down; Monkey takes out her minions and wraps her up afterwards.
- Fat Bastard: She is quite rotund and she tries to make a pelt out of Monkey.
- The Fashionista: She fancies herself one, and she makes her own clothes.
- Faux Action Girl: Without a ray gun or the element of surprise, she has no combat skills whatsoever.
- Nonhumans Lack Attributes: Not only does she have neither hair (anywhere) or genitalia, she also has no breasts and her large belly extends far beyond where her hips would go. Probably the only way the show got away with showing an adult (coded) female character getting stripped naked, Barbie Doll Anatomy or no.
- Talking Is a Free Action: Falls victim to this. When Honeydew interrupts their Cat Fight to deliver the episode's aesop, Peltra immediately stops fighting and just lets Honeydew rip off her hat and clothes, then give her a No-Holds-Barred Beatdown before Monkey arrests her.
- Shameful Strip: After Agent Honeydew ruins her plan by splashing paint on Monkey, she is then stripped naked and wrapped in sheets of metal.
- Unlimited Wardrobe: Has a wide variety of outfits, and wears a different one in each of her scenes.
- The Cape: Played for laughs - he tries to live up to his heroic principles, but tends toward obliviousness and narrow-mindedness.
- Captain Patriotic: He even hawks a snack named "Justice Fruit Pies", and periodically recites lyrics or lines from famous American works (such as the national anthem, the Constitution, and the Pledge of Allegiance).
- Chuck Cunningham Syndrome: Disappeared after the show was Un-Cancelled, along with the other Justice Friends. Though they did get an appearance in "Dexter's Wacky Races".
- Compressed Vice: His appearance in the The Powerpuff Girls episode "Members Only" showed he displayed traits of sexist behavior that was never displayed in this show otherwise he wouldn't have made Dee Dee his sidekick nor allow Miss Spell to join the Justice Friends.
- Crazy-Prepared: He wears dozens of masks to conceal his face."When I say secret identity, I mean secret identity."
- Eagleland: Type 1 (perhaps)
- Expressive Mask: His true face is never seen due to it always being concealed by his iconic golden mask.
- Expy: Captain America with Superman's powers and a personality similar to Space Ghost's.
- Large Ham: Major Glory takes this Up to 11.
- The Leader: Of the Justice Friends.
- Politically Incorrect Hero: His appearance in the The Powerpuff Girls episode "Members Only" makes him highly sexist towards the Powerpuff Girls by denying their request to join his team just because they are girls. His rude treatment of the Powerpuff Girls is also suggested to have ageist motivations because he also refuses to take them seriously just because they're young.
- Shipper on Deck: While they should, technically, be enemies, he encourages Krunk's attempts to woo She-Thing.
- Smug Super: He's pretty egotistical about his powers.
- Team Dad: He may also be the Team Mom depending on the situation.
- Took a Level in Jerkass: His appearance in the The Powerpuff Girls episode "Members Only", where he is portrayed as sexist and ageist towards the Powerpuff Girls and also isn't very nice to the other heroes on his team.
- Barbarian Longhair: Very long blond hair.
- Bare Your Midriff: His sleeveless shirt exposes his midriff.
- Bigger on the Inside: His room. There's an episode dedicated to it, appropriately titled "Valhallen's Room".
- Blinding Bangs: Has long hair that obscures his eyes.
- Chick Magnet: He has a bunch of wildly screaming female fans when he steps into the ring in "Wrasslor".
- Chuck Cunningham Syndrome: Disappeared after the show was Un-Cancelled, along with the other Justice Friends. Though they did get an appearance in "Dexter's Wacky Races".
- Empathic Weapon: His "Mighty Axe", a pink flying V-type guitar.
- Expy: Of The Mighty Thor.
- Improbable Weapon User: His mighty guitar.
- The Lancer: The more laid-back sidekick to the uptight Major Glory.
- Mellow Fellow: In contrast to Major Glory.
- Nerd: His true identity, which he reverts to when separated from his mighty axe for too long.
- The Power of Rock: He's the god of it!
- Only Sane Man: Similar to Dee Dee, in that while Valhallen's obviously not that smart, he's definitely got way more common sense than either of his teammates.
- Punny Name: "Valhalla" and "Van Halen".
- Shout-Out: To Van Halen, and Heavy Metal (mainly Heavy Mithril, what with his Viking motif) in general.
- Totally Radical: Most of his dialogue.
- Vague Age: He looks to be around his late teens to early/mid 20's, yet most of the time he acts more mature than Krunk and at worst, Major Glory. Not to mention that he is a god.
- Ye Olde Butcherede Englishe: The other part of his dialogue. He is a parody of the Mighty Thor, after all.
The Infraggable Krunk
Voiced by: Frank Welker
- Berserk Button: As Major Glory and Valhallen learn the hard way, don't destroy the TV while he's watching "Puppet Pals".
- The Big Guy: The muscle-man of the Justice Friends.
- Chuck Cunningham Syndrome: Disappeared after the show was Un-Cancelled, along with the other Justice Friends. Though they did get an appearance in "Dexter's Wacky Races".
- Dating Catwoman: He falls for his Evil Counterpart She-Thing, and the feeling is mutual.
- Dumb Muscle: Although he's more child-like than stupid.
- Expy: Incredible Hulk with reversed colours. Who coincidentally looks like another famously blatant Hulk expy.◊
- Gentle Giant: Despite being as big as the Hulk, Krunk is very friendly as long as he isn't mad.
- Hulk Speak: He's actually a parody of Hulk. Krunk speak!
- Manchild: Is a huge fan of the "TV Puppet Pals" show, to him it is Serious Business.
- Third-Person Person: He mainly speaks in third person.
- Dirty Communists: He's a stereotypical Communist Russian.
- Expy: He is most likely based on Marvel Comics villain the Red Skull, since he's a supervillain with "Red" in his name and is the main foe of Major Glory, himself a parody of the Red Skull's nemesis Captain America. The Russian theme may also be a nod to DC Comics character Red Star.
- Evil Counterpart: He serves as a villainous version of Major Glory.
- Heel–Face Turn: Appears among Major Glory and the other Dexter's Laboratory heroes as a member of hero team A.W.S.M. in The Powerpuff Girls episode "Members Only".
- Dating Catwoman: In spite of being on opposite sides in the war against good and evil, she and Krunk fall in love with each other.
- Distaff Counterpart: She is essentially a female version of Krunk.
- Evil Counterpart: For all intents and purposes, she's an evil equivalent to Krunk.
- Expy: She's what She-Hulk would be like if she were evil, dumb, and not related to the Hulk.
Voiced by: Maurice LaMarche
- Expy: A blatant Batman spoof. His origin even involves losing his parents after leaving a movie theater, albeit not in a way that gets them killed.
- Manchild: He is self-described as "a mere child of 30".
- Mr. Fixit: Much to his displeasure, the Justice Friends only let him join their team as their resident handyman, summoning him whenever they need him to repair something.
- Nerd Glasses: He's socially inept and he wears glasses.
- Raised by Wolves: Parodied. After his parents were scared away by rats when he was old enough to live on his own, the same rats took him in as one of their own.
Voiced by: Tom Kenny ("Rasslor"), Greg Eagles ("Last But Not Beast")
- Ax-Crazy: He attempted to mail a bomb to the President of the United States.
- Expy: He's a rather obvious parody of The Joker, since he's an insane criminal who has chalk-white skin, green hair, red lips, and a manic grin.
- Going Postal: He's a criminal who dresses like a postal worker and is completely crazy.