Originating from melon bread transformed by the nectar of a love flower into a heroine of justice, Melonpanna debuted in episode 200, "Melonpanna is Born," without a specific in-universe creation date. Her design features a dark green uniform, light green accessories, an orange-lined cape, and a distinctive cursive "m" insignia. Three diagonal lines cross her face, dominated by large green eyes.

Extreme kindness, sensitivity, and gentleness define her character. Despite possessing super strength, she actively avoids combat, prioritizing non-violent solutions. Her primary attack, the Melo-Melo Punch, induces temporary affection, dizziness, or awakens the deeply sleeping instead of causing harm. She also produces Melo-Melo Juice droplets from her head, capable of reversing Baikinman's "blackening" effect on allies, though its power weakens if Rollpanna's good heart falters.

Functioning as a peacekeeper and support figure within Anpanman's team, she participates in patrols and deliveries. Her vulnerability surfaces when Rollpanna's evil heart dominates, potentially causing Melonpanna to lose her sense of self. Melon juice serves as her essential energy source; deprivation leads to fainting. Cleverness occasionally surfaces in her actions.

Relationships shape her narrative profoundly. She views Anpanman as an adoptive older brother, interacting with him educationally alongside Creampanda. Rollpanna, her biological older sister, is deeply loved but rarely seen, causing loneliness; Melonpanna calms her during turmoil by calling her "sister." She treats her foster younger brother Creampanda with protective affection. Cheese the dog frequently accompanies her activities.

Her role extends beyond combat assistance. She serves as a nurturing figure and occasional teacher for younger characters like Creampanda, emphasizing kindness and courage. Flight capability enables her to respond swiftly to emergencies across the Anpanman universe.