Mūku is a supporting character in the anime Cosmic Baton Girl Comet-san who serves as the fairy companion of Princess Meteor of the Castanet Star country. Mūku travels with Meteor to Earth when she sets out to locate the missing prince of the Tambourine Star country. The character appears as a small, purple, circular bird-like creature with large eyes, a curled tail, and two small wings. Mūku is devoted to Meteor and acts as her constant partner throughout the mission on Earth, providing companionship and assistance as the princess searches for the prince while also navigating life in the human world. The relationship between Mūku and Meteor mirrors that of the protagonist Comet and her own companion Rababou, with the fairy serving both as a helper and as a link to their home star nations. Mūku does not undergo significant independent development over the course of the story, remaining a steady and loyal presence who supports Meteor through her interactions with the human characters she meets. The character's role is primarily supportive, aiding Meteor in her search and in the use of her star-powered abilities. Mūku does not possess notable independent abilities beyond those tied to Meteor's magic, and the character's function is closely aligned with the princess's own journey and growth throughout the series.