In One Piece, Chapter 817: Raizou of the Mist, there's a scene right after Luffy and his crew first encounter Raizou, where they all start asking him to perform some stereotypical ninja techniques.
In this scene, many different characters have requests that mostly parallel Naruto and old Japanese lore, seen in this panel:
Zoro asks for a different request, asking that the ninja "hide in the ceiling and get pierced by a spear".
This is the part I'm most confused about; what kind of reference is Zoro making when he asks for the ninja to hide in the ceiling and get pierced by a spear?