I don't think it was anyone else but me. Luffy said something while we were there, about other worlds and somehow we come and go. I dunno, don't look at me, I just know this isn't all that weird.

It was, uh. A colony, Cerealia. I don't remember if the world had a name or not. [he's doing that thing where he can willfully put unimportant details out of mind] It has lots of technology we don't but the downside was basically being lab rats under someone's control the whole time.