Carlos is jumpy and anxious, but with the skills of a true tech prodigy. He's been working feverishly on a project that would connect the Isle of the Lost to the outside world. Although he inherited his mother's love of fashion (especially if it's in black-and-white), he didn't inherit Cruella's love of dogs ― on the contrary, Carlos is deathly afraid of dogs (though it turns out this is because his mother told him dogs were rabid vicious animals that attack little boys who don't behave).
Instilled with an ever-present fear of dogs, Carlos joins the other villain kids as they take on prep school at Auradon to capture Fairy Godmother's magic wand and set their parents free. His tech-savviness comes in handy when he and the other villain teens get stuck in a bind.
Cruella raised Carlos into thinking that dogs are killers, as well as vicious, rabid pack animals. As a result, Carlos has an extreme fear of canines, practically allowing them to chase him up a tree.
In the film Descendants, Cruella forces Carlos to help touch up her roots, fluff up her fur, and scrape the bunions from her feet. This makes Carlos consider that heading to Auradon wouldn't be so bad, but Cruella uses his fear of canines as a way to control him. While in the limo headed to Auradon, Carlos takes a liking to chocolate. When they first meet Doug, he seems to have trouble remembering the names of the Seven Dwarfs, though Carlos seems to know the names of each and reminds Doug of Sneezy. He is the most tech-savvy, as he seems to take a liking to video games and is able to use a computer to locate the museum where the Fairy Godmother's wand is. When Jay causes the alarm to sound, Carlos hears the phone and picks it up. He manages to disable the alarm and make them think it was a system error.
The Fairy Godmother assigns Carlos and Jay to sports. While Carlos doesn't seem to do well, Ben offers to help him with this. As he practices sprinting, Carlos gets chased by the campus mutt, Dude. Seeing that Dude isn't vicious, Carlos starts to take a liking to canines, and takes Dude everywhere he goes in the film. During the big game between Sherwood, Jay insists that Carlos play with him, and with his help, the team wins the game.
When Cruella sees Dude and calls him an "earmuff," Carlos defends Dude; this is most likely the first time that Carlos has stood up to his mother. He then "burns" her by telling her to "give it a rest" with talking to a toy dog head. In one plan, it is Carlos' job to get into the limo and find the remote that activates the barrier around the Isle of the Lost. At the coronation, when Mal makes a speech on choosing to be good, Carlos is cautious at first, as he is nervous of the anger of their parents. But after being assured, he chooses to be good too. He is last seen dancing with Jay and Jane during the coronation party.
Carlos is returns in the animated short series Descendants: Wicked World and is voiced by Cameron Boyce, who also portrayed him in the live-action film.
He appears in "Careful What You Wish For" where he shows up at Mal's tent, moments after she accidentally rubs a lamp that causes herself, Evie, Audrey and Ben to be sent to the Isle of the Lost. He claims that Jay has just given him a smartphone, but is curious where everyone is before taking a selfie of himself.
Later in "Spirit Day", Mal and Evie try out for cheerleading and accidentally chant a spell that causes everyone to behave like dogs, minus Carlos. He reveals to Mal that he has the ability to speak dog, since he is the son of Cruella De Vil. Rather than immediately helping Mal, he decides to take pictures of Jay acting like a dog. Mal then gives him the spellbook to help her translate the reverse spell to Canine. When he does, Jay is not happy about the pictures and Ben allows him to chase Carlos across the field.
In the book, Carlos is treated badly by his mother and sleeps in her dressing room on the floor, which is filled with bear traps. He is forced to look after and clean her furs, and it is also revealed that she loves her furs more than him, and refers to her car as "her baby." He has a treehouse, and a cat named Beelzebub, and recites the periodic table to himself when he is nervous.
On the Isle of the Lost, Carlos is incredibly smart and enjoys science and creating inventions, and refers to himself as a nerd. He also has an intellectual rival named Reza in science class and Jace and Harry, the sons of Jasper and Horace, as his "minions", though they are not truly his friends since Cruella forces them to hang out together. He gets beaten up and pushed around in school, and Mal bullies him into holding her party at his house, before they became friends. Evie was also the first real friend he ever had and helps her escape his mother's dressing room when she was trapped in there as part of Mal's prank. Carlos was also the one responsible for making a hole in the dome briefly when he was testing his invention, which would cause Maleficent's staff to gain its magic back as a result. After Mal and Jay force Evie to help them retrieve it, she also convinces Carlos to reluctantly join the quest. Though the group fail when the staff is unable to retain any magic, Carlos is finally accepted by Mal and Jay, beginning the four's friendship.
According to the story Descendants: Return to the Isle of the Lost, Carlos' middle name is revealed to be "Oscar" and that he knows how to drive.
- Cameron Boyce dyed his hair just for this movie.
- Carlos' Tourney number is 101, an allusion to One Hundred and One Dalmatians, the film his mother is from.
- Carlos De Vil is Cameron Boyce's first role in a Disney Channel movie.
- Carlos De Vil was originally going to have two Dalmatian henchmen named "Laurie" and "Frieda"; this was scrapped because of the latter henchman name.
- Like Jafar, he appears to find his mother's talking to a stuffed dog head to be irritating
- Evie was his first real friend.
- He had a sidekick cat named Beelzebub (one of Lucifer's kittens). It was a gift in his baddie bag at Evie's 6th birthday party, and shows him affection his mother doesn't. Given there's no reference in the the film, this is likely a continuity error, or the cat had simply be adopted by someone else due to Cruella.
- He is extremely smart, as he managed to temporarily break through the barrier.
- He has a cousin named Diego.
- Cruella forced him sleep on a lumpy mattress in her dressing room, which is accessible through her fur coat closet. There is another door which Carlos use to bypass the bear traps security system.
- He considers Harry and Jace (sons of Horace and Jasper), his "fake" friends (henchmen).
- He re-purposes the various things in the basement (mostly dog stuff from her failed plan) for his science experiments, despite his mother's hysterical reactions to losing momentos of her past.
- He is treated far worse than Mal, Evie and Jay.
- While on the island, Carlos's mother used him as a slave, forcing him to do several things, even the humiliating act of doing her laundry because she was too lazy to do it herself.
- He attended Dragon Hall (an evil school), before Auradon Prep.
- The only colors that Carlos can be seen wearing (red, black and white) are also his mothers signature color's. Evie's first thought about what it made her think of was a bloody skunk.
- Evie gave Carlos his first pillow. He also considers her to be the sweetest girl he knows.
- In Disney Descendants Yearbook, his "secret wish" is to run a rescue shelter for abused and abandoned animals (and children), while his "not-so-secret wish" is to never see a fur coat or a bunion ever again.
- It's revealed that Carlos wants to be a dog walker or an app designer when he grows up.
- His favorite class is "History of Woodsmen and Pirates". Stating that there are very few dogs in those subjects(and not too many parents either).
- He likes to see D'Artagnan's sword, hat, and boots at the museum. Stating that D'Atragnan was one brave guy and that he really looks up to him.
- His mother loves her furs more than she loves him: this is something he knows, but when he is asked it as an answer to cross the bridge in the book, it makes him upset.
- In the book it states that seeing Jay happy made him feel very happy.
- As said by Cameron Boyce in an interview, he is more "I'm evil, don't hurt me!" and unlike the others does not actually do anything remotely mean-spirited throughout the whole movie and film, except helping with the plan, and perhaps kicking the apples in the first song. despite this, he is the last to choose good, but this is because of his fear of what their parents may do.
- Carlos resembles Kosuke Nitou from Kamen Rider Wizard.
- In Return to the Isle of the Lost, Carlos has started dating Jane and knows how to drive.
- In the same book, he says that while Maleficent can turn into a dragon, he considers his mother Cruella de Vil to actually being one.
- Carlos's middle name is Oscar.