Pokémon #104 in the National Pokédex.
"On its head, Cubone wears the skull of its dead mother as a helmet. ... It is called the Lonely Pokémon because of its tendency to keep to itself and avoid social situations, as it was apparently traumatized by the death of its mother. Cubone will often weep at night in mourning of its mother. When Cubone cries, the skull that it wears on its head vibrates and emits “a plaintive and mournful sound.” On the night of a full moon, the cries are said to be especially terrible. Cubone seems to recognize its mother in the moon, and so it howls with a particular sadness." 
Evolves into Marowak.
Japanese name: Karakara
-  Bulbapedia entry