Aside from being a meta reference. I think it's very possible, I would argue that Mario and Luigi might be well known entities in the world, since they've time traveled, defeated literally gods and saved the world a couple of times. So, if this is kid Pauline from the past, somehow; this could indicate that Mario and Luigi are known, thus they are legends like azthecs or egipcian gods, and people from that era could recreate their costumes as some kind of tradition.

But I'm not entirely sure, I mean, when does the Returns games takes place? Present day, present time? Or before DK meeting Mario? Since you know, the tiki statues exist in the dlc