Bokko, a young resident of Nandemoland, undergoes a dramatic transformation early in the story when Doringer's minions arrive. Struck by one of Black's bullets, which enforce animorphism, Bokko becomes a small songbird with distinctive pink feathers, mirroring the feminine attire worn before this change.

This transformation propels Bokko into a central role alongside Jim and the sentient locomotive Emma on their ensuing journey. Despite the avian form, Bokko retains full human consciousness and emotional bonds. The character's core motivation is a personal desire for restoration to human form, passionately expressed in the "I Want" song "Hayaku Ningen ni Modoritai".

Bokko actively contributes to the group's mission. During the final confrontation with Doringer, whose Cloak of Defense proves impenetrable to Jim and Emma's attacks, Bokko identifies and exploits a critical vulnerability. By successfully untying the cloak's fastening string, Bokko neutralizes its protection, enabling Doringer's defeat.

A mutual puppy love affection exists between Bokko and Jim, emphasized by the series' ending theme "I Love Pokko-Chan." Prior to transformation, Bokko's human life included typical childhood experiences like attending school, contrasting with Jim's tendency to skip.