Domo-kun and Nnke-kun are aliens planning to conquer the Earth. They are the first joke characters created by Oda. They first appeared in Oda's short story God's Gift for the Future. Later Domo-kun makes an appearance among the Buggy Pirates. Oda answered a question in an SBS and drew both of them. Nnke-kun appeared again alongside Pandaman on the cover of Volume 52.
(Source: One Piece Wiki)
Content compiled by AnimeList.moe from publicly available sources.
