The Hariisens resemble round, orange pufferfish with spikes around them.
The Hariisens only appear in the underwater areas of Twinkle Snow. In gameplay, they always float in one place. When the player approaches a Hariisen however, it will puff itself up, revealing spikes on its body and then fire said spikes in six directions. Once the Hariisen is spike-free, it will be vulnerable to the player's attacks. However, if left alone long enough, the Hariisen will regenerate its spikes.