Piidori is a pterodactyl and the closest companion to Nyago, the protagonist who transforms into the superhero Mighty Cat Masked Niyander. Raised by Nyago from infancy, Piidori shares a deeply loyal bond with him. He actively supports Nyago's heroic activities as Niyander, serving as a trusted partner during rescue missions and efforts to maintain peace in Cat Town. His primary responsibility involves delivering Nyago's transformation bag whenever Nyago is too far from home or has forgotten it, ensuring Niyander can appear when needed.

Piidori possesses flight capability, essential for swift aerial transport and assistance during emergencies. His verbal communication is limited to the sound "Pi!", though Nyago fully understands his intentions and expressions, underscoring their mutual trust.

Piidori displays bravery during confrontations, notably aiding against adversaries like HeHe Manto and Dokuro. He consistently serves as a devoted heroic ally, though one interpretation briefly suggested otherwise. Piidori appears exclusively within the main series storyline.