Melonpanna is Uncle Jam's creation, expanding the Anpanman hero family. Her body is melon bread, featuring a crisp cookie-dough exterior, soft interior, and signature criss-cross patterns atop her head. She possesses large green eyes, a small green nose, and orange hollow diamonds framing her face, marked by three diagonal lines on each cheek. Her attire includes a dark green uniform with a light green belt, gloves, and boots, plus a dual-colored cape (green top, orange underside) bearing a Cyrillic "m" insignia.

Her personality radiates extreme gentleness, sensitivity, and compassion, consistently demonstrating kindness with occasional cleverness in overcoming obstacles. She harbors profound devotion to her older sister Rollpanna, expressing intense longing when apart. This devotion can manifest as possessiveness regarding Rollpanna's attention and affection. While pacifistic and initially often rescued, she finds courage when allies, especially Rollpanna, are endangered.

Her key abilities involve the Melo-Melo Punch, incapacitating targets through overwhelming affection or euphoria without physical harm, also capable of awakening those in deep sleep. She generates Melo-Melo Juice from droplets on her head, typically reversing Baikinman's "blackening" effect on allies, though less effective when Rollpanna's "Flower of Pure Heart" weakens. Melon juice is her vital energy source; depletion causes fainting. Like other bread-themed heroes, her cape enables flight.

Her origin stems from direct involvement in Rollpanna's creation. Melonpanna actively requested Rollpanna as an older sister and contributed her own melon juice to Rollpanna's dough. Baikinman's sabotage introduced a "Baikin Plant" alongside the "Flower of Purity," resulting in Rollpanna developing dual hearts—one benevolent (red) and one malevolent (blue). This duality defines their bond; Melonpanna's presence or juice usually restores Rollpanna's benevolent heart when the malevolent one dominates, often triggered by Anpanman encounters. Conversely, Rollpanna's instability represents Melonpanna's significant vulnerability.

Within the hero team, she holds familial bonds, viewing Anpanman as an older brother and Creampanda as a younger sibling. She occasionally collaborates with Cheese on patrols and deliveries. Her narrative role frequently positions her as a catalyst for resolving conflicts involving Rollpanna's transformations. Her ability to neutralize Rollpanna's rampages, even against powerful heroes, establishes her as a stabilizing force despite initial portrayals of vulnerability.