One Piece: Season 1, Episode 18

1 - 18: You're the Weird Creature! Gaimon and His Strange Friends!

With Usopp now in the crew and a new ship, the Going Merry, under their command, the Straw Hats head to an island said to hold a fabled treasure, only to encounter a strange man stuck in a treasure box that has also been looking for this treasure.