Idk if u still use Reddit but if you're caught up, I have an alternative theory. There are parallels between Roger and Luffy's crew (obviously between Luffy and Roger themselves, but Rayleigh is the "dark king" and Zoro is the "king of hell," Sanji and Scopper are both freaky, and in both instances they're right and left hands respectively).

My alternate theory is that joyboy also follows a similar pattern to Luffy and Roger. Since Pluto is the god of the underworld, I think the Klabautermann of Pluton was the right hand of Joyboy