Mekao

Mekao (メカオ) is an old mechanic and shipwright from G-8 who shows great pride in his work. He becomes friends with Usopp and later helps the Straw Hat Pirates escape the base. Dr. Kobato is his daughter.

In the G8 Arc, Usopp explains to him what he saw next to the Going Merry back in Skypiea. Mekao was about to explain to him what he might of saw, but Drake pulled him away before he could do so. It is assumed that Mekao, like Franky knew that what Usopp saw was a Klabautermann. However he could not have said that it was a Klabautermann because at that time Oda hadn't yet revealed it and would only reveal it much later during the Water 7 Arc.

(Source: One Piece Wikia)