Cosmo is a kind, gentle, and empathetic plant-like alien from an endangered species, the Seedrians. She is characterized by her green skin, leaf-like hair, and flower-like features, as well as her soft-spoken demeanor. Despite her timid and sometimes fragile appearance, Cosmo possesses remarkable inner strength and a profound sense of self-sacrifice, driven by her desire to save her people and the universe from the Metarex. She is highly intelligent and sensitive to the emotions of others, often acting as a peacemaker. Her journey throughout the series involves overcoming her own fears and growing into a brave individual. She develops a very close bond with Tails, who often protects and encourages her.