Carlos is jumpy and anxious, but with the skills of a true tech prodigy. He has 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 is in black-and-white), he did not 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 do not 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 would not 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 does not 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 is not 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 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 "Neon Lights Out", Carlos and Jay arrive to explain that they got their carpet ride stolen. When Audrey notices they look roughed up, Carlos explains he did not get a chance to pick up his tux, which he describes as being white with large Dalmatian spots and calls it "Dog-Mazing".
The scene continues in "Hooked On Ben". While C.J. Hook explains what she has been doing in Auradon, Carlos mimics her while she's not looking, and after C.J. flees, Carlos joins the others for the group selfie.
In "Pair of Sneakers", Carlos and Jay are busy practicing for a tournament, where Carlos seems to be explaining the concept of baseball to Jay, based on hearing that "You get rewarded for stealing a base." Carlos swears on his mother's coat that he is telling the truth.
In "Talking Heads", Carlos is the first to defend Mal when Audrey accuses her of still being evil, and while everybody starts arguing, he tries to calm everyone down. He is then placed under a spell, along with everyone else, by Mal, forcing him to dance. Jay realizes that eating is able to break Mal's spell.
In "Steal Away", Carlos, Jay and Evie confront Mal on how she is behaving, after learning that she stole Jafar's staff from the Auradon Museum. Carlos is the first to suspect that a jewel, which Freddie Facilier gave Mal, is cursed. He also suspects that the jewel is what is forcing Mal to act evil, but he does not think Freddie knew of the curse. Mal apologizes with Carlos, Jay and Evie, forgiving her as she was under the influence of a curse. Though Jafar's staff is still in possession of Zevon, the son of Yzma.
In "Evil Among Us", Carlos, Jay, Freddie and Jane are rushing to the Jewel-BiLee as they are late; however, they notice Zevon trying to break into the throne room, where the jewels for the Jewel-BiLee are stored. Carlos calls out to Zevon, who revels himself to them, though Carlos and Jay seem to react to Zevon more with irritation than shock.
This continues in "Options Are Shrinking", where Carlos asks how Zevon was able to get off the Isle of the Lost. Zevon explains that he was able to slip through in the short time that the shield was open, when Mal was retrieving her birth right jewel. Carlos brings up that Zevon would have had to swim back to Auradon, but Zevon explains that C.J. was able to pick him up in her rowboat. When he learns that Zevon plans to take control of Auradon, Carlos rolls his eyes in doubt at this, but questions Zevon as to why. When Zevon explains his motives, Carlos, Jay, Freddie and Jane try to tackle Zevon, but one of his potions causes them to run backwards. Though they are able to counter this by running backwards towards the villain. Zevon uses another potion to cause them to spin on the spot, and then to shrink them down and imprison them in Jordan's (the daughter of the Genie) lamp (C.J. commenting how particularly little Carlos is). Their confrontation, however, did buy enough time, so by the time Zevon gets into the throne room, the jewels have already been taken to the Jewel-BiLee.
In "Trapped", Carlos seems to show that he is claustrophobic while trapped in the lamp. However, Freddie notes that because of their size, the inside of the lamp is larger than his dorm room. When Jane expresses concern that they will be missing the Jewel-BiLee, Carlos compliments how she looks. When Jay makes a crack about Carlos' size, Carlos tries to make a comeback but has issues in trying to think of one. When Jane tries to make some floating stairs using pillows and chairs, Carlos comments how "cool" it is. This affects Jane's concentration, causing the table he is on to turn into an inflatable kiddie pool. When Jay comments, "Nice," it then causes the table to turn to ice, which then causes Carlos to slip, breaking Jane's concentration and causing the floating stairs to collapse with Jay landing on Carlos.
In "United We Stand", Carlos, along with the others trapped in the lamp, are able to escape when the lamp is knocked from Jordan's hands (Jordan not realizing that they're inside). While still shrunk, they are able to trip one of Zevon's puppet soldiers, which in turn causes a domino effect on some other puppets. Zevon is defeated and Carlos joins the celebration while Mal announces the Jewel-Bi-Lee, even though he, Jay, Jane and Freddie are still shrunk.
In "Celebration", Carlos comments how Mal returned him, Freddie, Jane and Jay to their normal sizes, though Jay asks, "Why [is he] still small?" He is then presented with his jewel by Ben, with Carlos announcing, "I'd like to say a few words...AWESOME!" before he calls for the others to put their jewels together so the Jewel-Bi-Lee celebration can begin.
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 Return to the Isle of the Lost, Carlos' middle name is revealed to be "Oscar" and that he knows how to drive. The book also tells how he fancies Jane, daughter to the Fairy Godmother.
- 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 does not. Given there is no reference in the first 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 is two years younger than three of his VK friends: Mal, Evie, and Jay.
- He has a cousin named Diego.
- Cruella forced him to 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.
- Whenever Carlos is annoyed, he usually yells, "Dalmatians!" as Cruella would often use that as a curse word.
- 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 mother's signature colors. 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 is 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'Artagnan 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.
- 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 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.
- By the end of Descendants 2, Carlos is dating Jane.