Klabautermann

Klabautermann (クラバウターマン) is said to be a water spirit (or nix) who assists sailors and fishermen on the seas and in their duties. It is a merry and diligent creature, with an expert understanding of most watercraft, and an unsurpassed musical talent. One first appeared in Chapter 254 and Episode 167.

Appearance
A Klabautermann resembles a small humanoid sailor wearing a small dress and cap, and carries with it a small wooden hammer. This likeness is carved and attached to the mast as a symbol of good luck.

Story
The Klabautermann of the Going Merry was first seen during the Skypiea Arc, when Usopp saw it fixing the heavily damaged ship. The sharpshooter of the Straw Hat pirates overheard the Klabautermann telling the Going Merry that it would strive to make it fit for sailing the crew farther. It was spoken of briefly by Franky when he had kidnapped Usopp after he had temporarily left the Straw Hats crew. He revealed that a Klabautermann is a manifestation of a ship's soul brought about when it has been loved and cared for enough by its owners. It can be said that it was the Klabautermann of the Going Merry that spoke to the Straw Hats at the Going Merry's viking funeral.

Trivia

 * Strangely enough, despite not making much of an appearance, the Klabautermann was ranked as the 49th most popular character in the series (with 46 votes), 2 votes more than the Going Merry herself.
 * In real world myths, it is said to be a male seafaring spirit that aids ships of crews that truly deserve it, rather than being a ship's soul.
 * There is also one omen associated with it. That it only makes itself visible to the crew of a doomed ship. This is shown to be true in One Piece, as Usopp saw the spirit fixing Going Merry back in Skypiea, and in the end, due to various events occurring, Going Merry was broken beyond repair and had to receive her Viking Funeral.