Joke

Captain Joke is the main antagonist of the first TV special, "Adventure in the Ocean's Navel". Joke is a pirate captain who was after a treasure that allowed the holder to wish for anything they wanted; however, as he closed in on the treasure, his crew munitied and literally stabbed him in the back several times. However, for some reason he was turned into a bat and stayed in his body's remains, where he waited for ten years. After this time, the Straw Hats came along and unknowingly killed all the monsters holding Joke's other bones as he guides them to the treasure. The bones are then returned to his body upon their defeat, allowing him to revive and continue to look for the treasure. He is stopped by Hamu, the son of a chief elder that Joke killed. The Straw Hats (Luffy, Nami and Usopp) hold him down to keep from shooting Hamu with his multi-barrel pistol. As Joke crumbles to dust, he comments he wishes he had friends like them.

Trivia

 * Another undead skeletal pirate, Brook, would appear much later during the Thriller Bark arc. The difference between them is that Brook is a canon character while Captain Joke is a non-canon character.