The Hattifatteners are silent beings that are forever wandering around in large herds. The only thing that interests them is reaching the horizon – and once they reach it, they continue on their journey.
The white, faceless Hattifatteners are deaf and dumb. They don’t need to eat or sleep. They pack themselves tightly together in large herds, and stand there trembling. Nothing except roaming interests them.
The Hattifatteners resemble thin mushrooms. Their large, unfocused eyes change colour according to their surroundings. During thunderstorms, the Hattifatteners become highly charged with electricity and it’s a good idea to avoid them. You can sense their presence as an electrical charge in the air. At other times they’re harmless. Once a year, during a thunderstorm, the Hattifatteners meet in large numbers at the deserted Hattifattener’s Island. They become charged up with electricity and start glowing, rocking back and forth, and gather around a blue pole with a barometer attached to it.
On Midsummer day, the Hattifatteners gather on their own island for an annual meeting, after which they set out roaming once more. The Moomins first encounter the Hattifatteners in the book The Moomins and the Great Flood.