Not sure where to put this, but it seemed most pertinent to the anime (though I doubt it's a recording specifically for One Piece).
"Obake nante nai sa" ("There's no such thing as ghosts") is a children's standard in Japan. I'm not sure how many years old this particular recording is, but I got a kick out of it because I couldn't help but imagine Luffy singing it in Thriller Bark.
(There used to be a version on YouTube as well, but the account got deleted. Sorry, non-NicoNico people.)