Mepple hails from the Garden of Light as the chosen protector of the Princess of Hope, Mipple. This vital role fosters a deeply affectionate, "lovey-dovey" bond between them, expressed through frequent hugging and cuddling. Energy constraints within the Garden of Rainbows (Earth) force Mepple and Mipple to conserve power, residing primarily in compact, cellphone-like forms known as Card Communes, transforming only briefly into their true fairy selves. His appearance features lemon-yellow fur, striking navy-blue eyes with light blue highlights, bear-like ears, and a star-tipped tail, marked by an off-center male gender symbol on his head.

Personality-wise, Mepple exhibits arrogance tied to his status as a chosen warrior, demanding respect and preferential treatment. He clashes constantly with his equally stubborn human caretaker, Nagisa Misumi, their fiery tempers sparking regular arguments, yet he possesses a profound understanding of her feelings. His selfish nature manifests as constant demands for food, laziness, and open admission to manipulating Nagisa. However, he reveals genuine loyalty and gentleness solely with Mipple. This devotion curdles into jealousy towards Pollun, the Prince of Light, fueled by Mipple's protective attitude towards the prince and their shared royal lineage, frequently igniting arguments between the fairy pair.

Mepple's journey began with the Dotsuku Zone's assault on the Garden of Light. Sent to Earth alongside Mipple to find the legendary Pretty Cure warriors, a time zone disparity caused his arrival a century after Mipple. He bonded with Nagisa upon her discovery of him. Together with Mipple and Honoka Yukishiro, they confronted the Dotsuku Zone servant Pisard. Mepple and Mipple empowered Nagisa and Honoka to become Cure Black and Cure White. Residing with Nagisa throughout the initial conflict, Mepple aided her while masking his physical deterioration in the Garden of Rainbows behind spoiled behavior. A defining moment saw him risk his life shielding Mipple during Ilkubo's attack, urging her to uphold hope as the Princess of Hope.

Following the Dark King's defeat, Mepple and Mipple faced separation from the girls to return to the Garden of Light, avoiding eternal sleep on Earth. Choosing instead to stay with Nagisa and Honoka, they accepted eternal sleep, their forms deactivating into inert cellphones. In *Futari wa Pretty Cure Max Heart*, Mepple and Mipple awakened to assist Pretty Cure against a new threat targeting the Queen, upgrading to Heartful Communes that unlocked new transformations. During the final battle against the resurrected Evil King, Mepple declared he regretted nothing about meeting the humans, strengthening Pretty Cure's resolve. After the Evil King's defeat, the mascots initially departed silently but returned permanently when granted safe existence in the Garden of Rainbows, solidifying their bond.

Within the movie *Futari wa Pretty Cure Max Heart 2: Yukizura no Tomodachi*, Mepple accompanied Nagisa on a skiing trip. He criticized her snowboarding practice and sensed the dark presence of antagonists Freezen and Frozen. He journeyed to the Garden of Clouds following the discovery of the phoenix chick Hinata. Amidst the conflict, he witnessed Frozen manipulate Cure White into fighting Cure Black, causing temporary discord between Nagisa and Honoka before their reconciliation and teamwork defeated the darkness threatening Hinata and the Garden of Clouds.

Mepple consistently ends sentences with "-mepo" in original language versions. His relationship with Nagisa evolved from constant conflict to mutual reliance, underscored by his distress over potential permanent separation and his ultimate choice to stay with her in the Garden of Rainbows.