Hattifatteners are pale, tall, strange creatures which grow from seeds. They look just harmless or even cute to some eyes, but actually it is very dangerous to get closer to them, especially when they are electrically charged.
In the game a hattifattener doesn't seem to care about you, moves randomly and restlessly emits lightning bolts in random directions.
Killing a hattifattener causes some serious static discharge. It doesn't leave a corpse nor a barometer.