This is officaly one of the Puffle Hats. The Propeller Hat is also a toy and is also a item. The Green Puffle's wear this item as the toy. Some other penguins might want to match their Green Puffle, so they wear the Propeller Cap. which is not noted as hat in the inventory though. You can get this from the catalog. It is very likely that only the green species will wear it. though some others like it too.