Because it never removes its skull helmet, no one has ever seen this POKéMON's real face.
Wears the skull of its deceased mother. Its cries echo inside the skull and come out as a sad melody.
If it is sad or lonely, the skull it wears shakes, and emits a plain tive and mournful sound.
It always wears the skull of its dead mother, so no one has any idea what its hidden face looks like.
It lost its mother after its birth. It wears its mother's skull, never revealing its true face.
— Pokédex entries (via PokeAPI)