Melonpanna, born from Uncle Jam's bakery for the Anpanman universe, possesses a head crafted entirely from melon bread, its surface etched with a distinctive grid pattern mirroring the pastry's cookie crust. She wears a dark green uniform accented by a light green belt, gloves, and boots, alongside a cape displaying green outer fabric and vibrant orange lining. A cursive "m" adorns her chest. Her face features large green eyes, a small green nose, orange diamond-shaped cheek markings, and three diagonal lines crossing her features.

Her nature radiates exceptional kindness, sensitivity, and a deeply nurturing spirit, typically expressed through gentleness. Though conflict is anathema to her, she wields super strength and will fight fiercely to shield others. Moments of vulnerability sometimes lead to her rescue by allies like Anpanman or Rollpanna, yet she reveals profound resilience when circumstances demand it.

Melonpanna's powers include the Melo-Melo Punch—a unique, non-injurious strike that induces affectionate paralysis in foes or rouses individuals from deep slumber. She also secretes Melo-Melo Juice from her head; these potent droplets cure allies afflicted by darkening or corruption, such as Baikinman's influence. This healing proves ineffective only when Rollpanna's inherent goodness suffers fundamental compromise. Like fellow bread-headed heroes, she possesses flight.

Key relationships define her journey. She views Anpanman as an older brother, frequently seeking his protection and guidance. Her deepest familial bond is with Rollpanna, cherished as an older sister despite Rollpanna's later creation. This connection is marked by intense affection and longing, as Rollpanna maintains distance to shield others from her unstable dual-hearted nature. Melonpanna uniquely counters Rollpanna's evil impulses, restoring her to goodness. She also shares a close, sibling-like rapport with Creampanda, often acting as his protector or mentor.

Within the "Yumeneko no Kuni no Nyanii" narrative, Melonpanna's compassion drives pivotal events. Sharing a collective dream during a comet's passage, she discovers and rescues an endangered egg. This egg follows her into the waking world, hatching into the kitten Nyanii, with whom Melonpanna forms a strong maternal bond, nurturing her devotedly. The plot escalates when Baikinman inadvertently awakens the ancient monster Muuma, coinciding with the revelation of Nyanii's true origin as a being from the comet world. Facing profound emotional turmoil upon learning Nyanii must return to her home world to survive, Melonpanna participates in resolving the conflict with Muuma, striving to ensure Nyanii's safe departure.