Medama-Oyaji is a recurring character in GeGeGe no Kitaro, serving as Kitaro's father and a key ally in the series. He is a small, one-eyed yōkai who lives inside a tiny body shaped like an eyeball, often providing wisdom, guidance, and comic relief. Despite his unusual appearance, he is highly knowledgeable about the yōkai world and helps Kitaro deal with supernatural threats. His role is both supportive and advisory, making him one of the series' most recognizable characters.