One Piece: Nenmatsu Tokubetsu Kikaku! Mugiwara no Luffy Oyabun Torimonochou

This end-of-year special drops the Straw Hats into a wild alternate reality: an Edo-flavored version of 19th-century Japan called the Grand Jipangu. Here, Luffy and Usopp are crime-fighting detectives, Nami and Sanji run a restaurant, Zoro is a wandering monk, and Chopper is the town doctor. The story splits into two halves: first, Buggy the Clown and his family terrorize the town by seizing shops, forcing Detective Luffy to step in. Then a mysterious wounded girl named Vivi turns up, and Buggy comes hunting for her secret. It is pure comedic what-if fun, gleefully reshuffling the whole cast into period-drama roles for a one-off adventure.