Who is fixing the Going Merry? Recently got done watching the Skypiea Arc, and it has just been bugging me constantly, but in Episode 167 Usopp goes to the bathroom and sees someone fixing the Going Merry. No where else is this addressed in the Arc (at least anime-wise): was Usopp just seeing things because he was tired or was there really someone fixing their ship for them?

Here is a picture of the scene I am talking about:
It was fixed by a Klabautermann.


  A Klabautermann is said to be a water spirit (or fairy) that dwells on ships and is basically an incarnation of a ship that has been well cared for. It is a merry and diligent creature that is said to warn sailors when a ship's in danger and help in bigger ways sometimes. They are normally considered to be only a legend among seafarers.


It is explained later in Episode 247 (Chapter 351 of the manga)


   Franky hears by Usopp about what happened to the ship and in particular to the fact on Skypiea you mentioned and explains him about that creature he knows from legends.


For more information about the klabautermann folklore itself you can look at its Wikipedia page.