Born from melon bread animated by the Flower of Love's nectar, Melonpanna embodies a heroine of justice with profound kindness. Her appearance features a dark green uniform accented by a light green belt, gloves, shoes, and a cape (green top, orange underside), marked by a distinctive cursive "m" insignia on her dress. She possesses large green eyes, a small green nose, and three diagonal lines crossing her face. Melonpanna stands shorter than many allies yet taller than figures like Akachanman and Creampanda.

Gentleness, empathy, and sensitivity define her core personality. She avoids conflict but finds courage when protecting others. A deep emotional bond with her sister Rollpanna shapes her character profoundly; Melonpanna frequently expresses loneliness due to their separation and acts as a stabilizing influence for Rollpanna's volatile dual-hearted nature. Despite being biologically older, Melonpanna regards Rollpanna as her elder sister, fulfilling her expressed desire for an older sibling.

Her signature Melo-Melo Punch emits a non-harmful effect, disarming foes by inducing affection or lethargy and awakening individuals from deep slumber. She produces Melo-Melo Juice from her head, droplets capable of reversing villain-induced "blackening," though its power wanes without Rollpanna's good heart energy. Like other bread heroes, she possesses flight capabilities.

Key relationships include protectively treating her adoptive brother Creampanda and assisting Anpanman during patrols and deliveries. Her bond with Rollpanna remains paramount: Melonpanna's presence or voice can suppress the evil heart in Rollpanna, a condition stemming from Bacteria Grass introduced by Baikinman during Rollpanna's creation that split her heart into red (good) and blue (evil) halves.

Across media, her non-confrontational nature often leads to situations requiring rescue, frequently prompting calls to Rollpanna for aid. In "Yūreisen o Yattsukero!!", she and Rollpanna jointly confront challenges aboard a ghost ship manipulated by Baikinman. In "Ringo Bōya to Minna no Negai", she appears within the ensemble responding to events. Her vulnerabilities include dependency on melon juice as an energy source, causing fainting without it, and susceptibility to fear, notably triggered by encounters with figures like Houtaiman.