Episode 221

"The Mysterious Boy With the Whistle and Robin's Guess!" is the 221st episode of the One Piece anime.

Short Summary
Robin suggests that only those who were sleeping lost their memories. Luffy and the others then remember seeing the mysterious boy who played some kind of flute. Later that night, they discover the boy outside and Luffy tries to fight him. At the last second, he proclaims his memory has returned.