^ I dunno, that's what appeals to me personally. =3 I'm really enjoying a horror story from the SHs' point of view and in Oda's stylings.
Ah, but you're forgetting how in Water Seven, even Sanji and Zoro initially mistook Kaku for Usopp – so it's possible that Perona has mistaken Usopp for someone else too. Maybe he thinks Usopp is Kaku!
Even in the Arlong arc, he was mistaken for a fishman. xD