Carlos Lopez first appears in the animated series Transformers: Armada as a young boy who becomes an ally to the Autobots, and his story continues into the sequel series Transformers: Energon. By the time of Energon, which takes place ten years after the original conflict, Carlos has grown older and his role has evolved accordingly. He is no longer the school-aged skateboarder from the earlier series but is instead a young adult serving as a crew member aboard the Earth Federation's space station orbiting Mars. His long history with the Transformers, having been present for the initial arrival of both the Autobots and Decepticons on Earth, cements his place as a trusted human ally within their network.

Carlos's personality reflects his background as a seasoned observer of intergalactic conflict. He maintains a level-headed and practical demeanor, often acting as an operator or communications relay. His character is known for his distinctive exclamation, "Holy frijoles," a phrase he uses in moments of surprise or crisis, which he utters during the Terrorcon attack on the Mars space station. While his primary interest as a child was skateboarding, supplementary materials from the Transformers franchise indicate he has a keen interest in hip-hop music and possesses notable mechanical skills, being characterized as an excellent mechanic. Although this specific aptitude is emphasized more in Dreamwave comic publications than in the Energon animated series itself, it forms an important part of his broader character profile.

Carlos’s motivation for remaining involved with the Autobots stems from his long-standing loyalty and sense of responsibility. Having witnessed the war between Autobots and Decepticons from its early days, he understands the stakes of the conflict and chooses to contribute to the protection of Earth. His role in the Energon storyline is that of a support operative, using his position on the space station to monitor alien activity, broadcast warning signals, and relay intelligence to Autobot forces on Earth. During a surprise attack by Alpha Quintesson's Terrorcons, Carlos is on duty at the station, where he witnesses the assault and attempts to coordinate a response.

His key relationships are rooted in his past. He is part of an original trio of humans from Armada, alongside his longtime friends Rad White and Alexis Thi Dang. This friendship dates back to kindergarten, and their shared experiences form the core of their trust in one another and in the Autobots. In Energon, the three friends remain connected, often working together or appearing in the same locations, such as when they join forces with the Dinobots to pursue a captured Kicker or when they are together observing the departure of ships at the end of the series. Carlos also has a history of partnership with the Mini-Con known as Grindor, a member of the Street Action Team. While Grindor does not play a prominent role in Energon, this partnership was central to his character in the earlier Armada storyline.

Carlos experiences significant development between the two series, transitioning from an impulsive and sometimes reckless child who frequently found himself in danger to a composed young adult operating in a professional capacity in space. In Armada, he was prone to triggering traps or sneaking Mini-Cons into public places, actions that required him to craft excuses to avoid suspicion. By Energon, his impulsivity has tempered into a reliable ability to act under pressure. While the animated series focuses on his role in communications, the character is also noted for his adaptability and bravery, having previously rescued animals during wildfires and survived capture by Decepticons such as Cyclonus and Megatron. His notable abilities include his proficiency with mechanics, his skills in sports and skateboarding, and his extensive knowledge of Transformers history and technology, which makes him a valuable asset to the human-alien alliance.