The Harry Potter reference in One Piece hints at the existence of the wizarding world in the manga.

One of the most well-known aspects of mangaka Eiichiro Oda’s process in crafting his One Piece story is pulling from real-world historical ... a key historical reference (Image via Shueisha ...

The 'Will of D' is one of the biggest mysteries that One Piece hasn't given any hints ... of the Ancient Kingdom's reality, as well as a reference to the Kingdom to Impel Down.