Hoi Hoi is one of three feline scientists dispatched from the cat world of Banipal Witt by Master Sandada. Their mission is to locate and retrieve the human children Toriyasu and Meeko, bringing them to Banipal Witt to rescue their transformed dog, Papadoll. Hoi Hoi undertakes this task alongside fellow scientists Henoji and Suttoboke.

Hoi Hoi possesses an anthropomorphic feline appearance, consistent with Banipal Witt inhabitants. The character demonstrates technical proficiency by operating specialized transport crafts capable of interdimensional travel between the human world and Banipal Witt. During the mission to infiltrate Princess Buburina's castle, Hoi Hoi joins the rebels' efforts alongside Toriyasu and resistance fighters, navigating the castle defenses and aiding the plan to stop Buburina and restore Papadoll.

Hoi Hoi exhibits a mediating presence within the group. When Toriyasu argues with ChuChu, Hoi Hoi intervenes to prevent conflict, offering context about the cultural significance of Banipal Witt's moon and revealing a deeper understanding of their world's lore.

Following the successful defeat of Princess Buburina and Papadoll's restoration, Hoi Hoi returns the children to the human world. However, Hoi Hoi and the other cats reappear shortly after, signaling an unresolved matter. No additional background story, character development, or involvement in other media beyond this film is documented in the provided information.