The Penguin Hats are mediums that allow Himari Takakura and Mario Natsume to continue living in return for the retrieval of the Penguin Drum. The hat resembles a Rockhopper penguin. There are two Penguin Hats and they were created when Momoka Oginome had a curse put on her by Sanetoshi Watase.
People Who Have Worn a Penguin Hat
When it's worn by Himari, the Princess of the Crystal possesses her, wearing a black and white, penguin themed outfit that is very similar to the stage outfits that Double H wear. Sometimes the hat is nowhere near Himari but simply appears on her head when the Princess has to speak with Shoma and Kamba. When she is channeling the princess, Himari's eyes become a bright pink colour and also change shape.
Mario Natsume wears a similar penguin hat. His is blue where as Himari's hat is yellow. It also has a little crown atop its head. There are hardly any scenes in which Mario is seen wearing the hat, and the few scenes that do show so are very brief , so it is hard to tell what the entity that possesses him is like. Though it can be inferred that it is not the Princess of the Crystal as well, because it seems to act more reserved than the Princess in Himari's body is.