[ How does he explain this one... Well, can't really say that he has named after his Personas so he's going for second best: ]

I name all of my Pokemon after mythological figures. You're a pretty much a legendary hero in the Celtic folklore.

I've just been reminded of you when I've thought of what Riolus evolve into. [ Yeah, Souji, butter him up so you might survive, though this is pretty much the truth. ]