Dexter is the main character and protagonist of the Dexter's Laboratory. He is a boy genius who has a secret laboratory. His intelligence makes him the brains of the family. He is always working on new inventions and creations every day, but his stupid sister Dee Dee is always breaking into his lab and destroying his work. The plots of this show mainly revolve around his relationship with his sister and everything that happens between the two. He is currently being voiced by Candi Milo and was formerly being voiced by Christine Cavanaugh before she retired.
Dexter was first born in a hospital in Huber. His Dad was so happy to have him until he found out that he had a very large head. He was terrified and hoping that there was nothing wrong with him. The doctors studied this and they found out that the reason for this was because he was a genius. His Mom and Dad were very happy to hear this and were very proud of him. The doctor gave him glasses in honor of his genius. Then, his parents took him home.
Dexter immediately got to building inventions and studying science and developed so quickly, but Dee Dee kept on wrecking his inventions. This carried on until Dexter was 7 years old. Then, he found a secret place in his house that was empty and undiscovered. He decided to make this his secret laboratory and he would use it as a way to stay away from Dee Dee. One day, Dee Dee was playing in Dexter's Room while he was in his lab and then she saw the bookshelf that led to his lab. She was confused as to why it would be there, she pulled a book out and discovered Dexter's Lab. This was how she first found out about it. Ever since then, Dee Dee had always been annoying him in his lab.
When Dexter started going to school at Huber Elementary School, he was always the smartest kid there and the favorite of all his teachers. All of the teachers loved him and treated him like a friend. The other kids were jealous of him being so smart. This was all until a new kid came to the school when Dexter was going back to school again for a new year after summer break. The new kid was a kid named Mandark who became his rival. Mandark was smarter than him and the teachers all loved him more. Dexter showed Mandark his laboratory thinking it would mean that he's smarter than him, but then Mandark showed that he had a bigger better laboratory. Dexter thought that it was all over for him until Mandak fell in love with his sister Dee Dee. Dexter had the idea to send Dee Dee over to Mandark's Laboratory where she destroyed it just like she destroyed his laboratory all the time. After this, Dexter had officially become smarter and Mandark was always his eternally one-step-behind rival.
When Dexter became a teenager and he grew up to get a job, Mandark had taken over the world and he made everyone work as their slaves. He gave a number to all of them and Dexter's was Number 12. Number 12 was terrified of Exectutive Mandark and Exectutive Mandark always abused him because he hated him the most. Dexter, back when he was a kid before this had happened, used a time machine to travel into the future to see this in the movie Ego Trip, when he saw himself like that. He convinced him to overthrow Mandark, so they went into the future and there they found Action Dexter, who was Dexter as an adult in the future. This was when Mandark had taken over the whole entire world. They also found Old Man Dexter who was Dexter as an old man.
The four of them teamed up to destroy Mandark and have Dexter take over the world. After this, all of the Dexter's returned to their normal times again. So in the end of Dexter' life, when he was an old man, he had taken over the universe and made it for good, and had made the amazing universe a wonderful place for mankind to live with his vast and unlimited knowledge technology and science.
Dexter is a very short young boy who has curly red hair that was passed down to him from his mother, a pair of glasses that appear semi-circular at normal times, but when he widens his eyes, the tops of them round out. He wears a little white lab coat with black buttons on it. He also wears purple gloves, and a pair of black rubber zipper boots. He speaks with Russian accent despite the rest of his family not having any accents.
Dexter is an extremely intelligent boy (a self described "Boy Genius") who has been creating fantastic inventions since he was a baby. He considers Albert Einstein to be his greatest influence. He is normally in conflict with his sweet 15-year-old sister Dee Dee. Dexter, though highly intelligent, often fails at what he has set out to do when he becomes overexcited and makes careless choices. He manages to keep the lab a secret from his clueless, cheerful parents, who amusingly never notice any evidence of the laboratory, even when it was right before their eyes. Despite coming from a typical all-American family, Dexter speaks with a Russian accent, a reference to Tartakovsky's own accent that he spoke with during childhood and prank calls Rob Renzetti sent to Tartakovski while the two were at CalArts. Dexter's favorite superhero is Major Glory. In Rude Removal, his counterpart is very rude and highly disrespectful to his mother.
In the What-A-Cartoon shorts, Christine Cavanaugh served as the voice of Dexter, and returned to voice the character when the show was picked up, and remained on the show throughout the first two seasons, and the first few episodes of season 3. However, Cavanaugh retired from voice acting after the season 3 premiere, and was replaced by Candi Milo, which some fans did not immediately take to heart, as they claim she made Dexter's voice sound forced and cheesy. However, they noted an improvement in her rendition of Dexter in Season 4.
- "Dee Dee" - Various Episodes
- "Ahhh, what a fine day for SCIENCE!" - Various Episodes
- "Dee Dee! Get out of my laboratory!" - Various Episodes
- "At last, my greatest creation is now completed!" - Various Episodes
- "Dee Dee No! Don't push that button!" - Various Episodes
- "This is not for you, this is for my laboratory rats." - The Big Sister
- "SHUT UP! SHUT UP! SHUT UP!" - Monstory
- "This better be important woman, you are interrupting my very delicate calulations." - Dee Dee Dimensional
- "Nothing! Nothing! You only see air!" - LaBretto
- "Ahhh, what a wonderful day for I Dexter, boy genius to be working in my laboratory." - Opposites Attract
- "One ... child and one adult please" - Comedy of Feathers
- "Yeah, whatever." - Comedy of Feathers
- Dee Dee - Dexter is normally in conflict with his sweet older sister, Dee Dee, who always mysteriously gains access to his lab no matter what he does to try to keep her out. Dee Dee eludes all manner of security and, once inside, delights in playing in the lab, often destroying all of his creations and often by pushing the wrong buttons on an invention. This is often preceded by Dee Dee asking "Oooooh, what does this button do?," without waiting for an answer. Despite her hyperactive personality, Dee Dee sometimes makes more logical decisions than Dexter, or even gives him helpful advice. Despite being excessively irritated with Dee Dee with her constant interference and her stupidity, Dexter still loves her and cares about her well being, and even saved her life numerous of times.
- Mandark - Dexter has a big rivalry with Mandark. He hates him because he constantly tries to shut down or destroy Dexter's lab and prove that he is smarter than him. Although Mandark isn't as recurring of a conflict as Dee Dee is, Mandark is even worse of an enemy than Dee Dee is. They sometimes compete to see who's smarter and Dexter always wins, although sometimes they both get tied for instance in the episode where Monkey and Quackor were both fighting and Dexter and Mandark were going to turn them into class.
- Monkey- Dexter is always trying to make Monkey do something amazing but no matter what he does to him Monkey just stays as a normal old monkey, But whenever Dex isn't looking, monkey changes into an amazing superhero and that power somehow is subliminal to all of Dexter's most observant and flawless of machines.
- Dad - He is his father, normally tends to show favoritism to Dee Dee for her athletic prowess, but will occasionally side with Dexter when facing a challenge between the sexes. Dad is also depicted as unreasonably hostile towards Dexter when he interferes with a sports-related activity such as watching the "biggest golf match of the year" or breaking his bowling trophy.
- Mom - She is his mother, appears to be fairly close to his mother, and appears to have inherited his intellect from her. He is sometimes embarrassed by her, such as when she kept causing a ruckus at a chess tournament in an effort to cheer him on and ended up getting him disqualified.
- Douglas E. Mordecai III - Douglas E. Mordecai III is Dexter's closest friend. He is a genius just like him, although Dexter is so much more smarter because Douglas doesn't have a secret laboratory (at least not that we know of) so Douglas is only a nerd while Dexter is more of a super genius.
- Koosalagoopagoop - Koosy is always annoying Dexter. Dexter thinks Koosy is stupid and all of his little jokes and antics are stupid and make no sense. Dexter also promises to keep Koosy a secret from Dee Dee's parents just like she keeps his laboratory a secret from them.
- Major Glory - Dexter is a huge fanboy of Major Glory. He is seen watching his show, reading his comic books, playing with his toys, and loving everything that's related to him. Major Glory is Dexter's entertainment idol. Dexter has even met Major Glory in person on certain occasions such as the episodes Star Spangled Sidekicks and Figure Not Included.
- Action Hank - Next to Major Glory, Action Hank is an iconic character that he is obsessed with and has a vast love for. Dexter loves watching Action Hank's show and wants to be just like him. He has met him in person in the episodes Action Pack, A Beard to be Feared and Decode of Honor and the two of them are good friends that know each other well.
Cartoon Network Punch Time Explosion
Dexter is a playable character in this game. He is also the one who helps save the other characters from their dimesions by using an invention of his to travel to the other dimensions and save them. He uses his inventions to fight people and his super attack is the Robo Dexo 2000.
- Dexter's voice actor is Christine Cavanaugh and Candi Milo in the series, but in Cartoon Network: Punch Time Explosion, it is Tara Strong, who is the voice of Bubbles from Cartoon Network's The Powerpuff Girls.
- Dexter's last name has never been revealed throughout the entire series.
- In the episode Go Dexter Family Go!, Dexter says his favorite color is orange, but in a previous episode he stated his favorite color was blue.
- In Ego Trip, his teenage self and his old man self didn't have Russian accents like he did, however his adult self did.
- In seasons 1 and 2, Dexter had a longer hear and a double chin and there were two visible buttons on his lab coat, but in seasons 3 and 4, he had a shorter head, no double chin, and had only one visible button.
- Dexter speaks with a Russian accent, although the rest of his family doesn't.
- Dexter's astrological sign was first shown to be Capricorn in the episode "A Hard Day's Day," but since he was born around in the end of March, he is actually Aries.
- Although Dexter is the main character, there have been many episodes where he has not appeared.
- Dexter has made many cameos in episodes of The Powerpuff Girls. The reason for this is possibly because the creator of The Powerpuff Girls, Craig McCracken helped with making Dexter's Laboratory before he created The Powerpuff Girls.
- In the episode "Powerpuff Bluff" Dexter was seen sleeping with the other kids at Poakey Oaks Kindergarten.
- In the episode "Criss Cross Crises" when Professor Utonium was switching peoples bodies trying to turn them back, one of the people Mrs. Bellum switched bodies with was Dexter.
- In the episode "Forced Kin" when it showed the people that were looking up at Mojo Jojo's giant robot, one of them was Dexter.
- In the episode "Ploys R Us", Professor Untonium was seen getting a stuffed toy of Dexter as well as stuffed toys of Dee Dee and Monkey.
- In the episode "Dexter's Wacky Races" Dexter had a car that he invented in his laboratory that he was using in a race that has his parents in it. This means that he was exposing something from his lab to his mom and dad, although he and his parents were never directly in front of each other nor did they make any interaction with each other in the episode.
- In the episode "Tribe Called Girl", Dee Dee said that Dexter had special needs, however this may have been done out of her stupidity so it may be possible that this is not true.
- Dexter's glasses are flat on top when he is feeling content or angry, but when he is shocked or scared, his glasses become rounded at the top.
- In the episodes "Old Man Dexter", "Ego Trip", and "Bygone Errors" Dexter's old man self didn't seem speak with a Russian accent anymore.
- Dexter's russian accent is a reference to the accent Gennedy Tartakovski used to speak with when he was a little kid.
- He has appeared in a variety of Dial M for Monkey episodes such as, Magmanamus, Peltra, Simion, and Last But Not Beast.