Charles is a female Exceed, a small, white-furred, cat-like creature from the parallel world of Edolas, who serves as the steadfast partner and closest friend of the Dragon Slayer wizard Wendy Marvell. She was sent to Earthland as an egg and was discovered and hatched by Wendy, a bond that has defined her entire existence. Her appearance is distinguished by her small stature, pink inner ears, brown eyes, two whiskers on each cheek, and a signature pink bow tied around her tail. Like all Exceeds, she possesses Aera, the magical ability to grow wings on her back for flight, which she uses to carry Wendy and provide aerial support.

In stark contrast to the more carefree and emotional Happy, Charles has a personality characterized by seriousness, prudence, and a haughty demeanor. She often appears strict, uptight, and quick to scold others, particularly when she perceives them as foolish or undisciplined. This was especially evident when she first joined Fairy Tail, as she reacted with visible displeasure to the guild's notoriously loud and chaotic behavior. Her primary driving motivation is an intense, almost maternal desire to protect Wendy, whom she views as someone who needs guidance. She is keenly aware of Wendy's shy and gentle nature and often pushes her to be more confident, even if Charles herself struggles with sociability.

Charles plays a crucial role as both a guardian and a strategist for her team. Her most significant narrative function unfolds during the Edolas arc, where her mysterious past and true nature are revealed. She initially believes that her kind were sent to Earthland with a mission to kill all Dragon Slayer wizards, a fact that causes her immense psychological torment given her deep love for Wendy. This burden is later revealed to be a lie constructed by Queen Shagotte of Extalia. The queen, who possesses the power of precognition, foresaw the destruction of their kingdom and sent the unhatched Exceed children to Earthland to save them. Charles learns the shocking truth that she is actually the princess of Extalia and the daughter of Queen Shagotte, having inherited her mother's ability to see the future. This precognitive power initially manifests as unwanted and distressing visions, but she gradually learns to manage it, enabling her to foresee danger and aid her allies.

Key relationships heavily influence Charles's development. Her bond with Wendy is the core of her identity, and her protective instincts are her defining trait. Her relationship with the male Exceed Happy evolves significantly over time. Happy, smitten with her at first sight, persistently pursues her affections, and for a long time, Charles rejects his advances and dismisses him as useless. However, during the events in Edolas, Happy's bravery, loyalty, and determination to protect her cause Charles to soften. She begins to show genuine warmth towards him, and their relationship matures into one of deep mutual trust and respect, with subtle hints of romantic affection. Initially aloof towards the rest of Fairy Tail, her experiences in Edolas help her open up, and she grows to genuinely care for her guildmates.

Over the course of the series, Charles undergoes significant personal development. After the Edolas arc, she no longer carries the false burden of a killer's mission and accepts her powers and heritage. Later, through dedicated training, she learns transformation magic. This allows her to assume a humanoid teenage form with shoulder-length white hair, retaining her cat ears and tail. In this form, her magical abilities and precognitive powers are enhanced, and she becomes more proficient in hand-to-hand combat. While she primarily remains a support-oriented fighter, her journey transforms her from a paranoid and emotionally reserved guardian into a more confident and openly caring individual who has found a true home and family within Fairy Tail.