one thing i've always considered is that how is vivi able to have children? i mean, he's supposed to be a machine right? does he produce sperm or something? and also, we know that he and eiko sort of had something going on, but his children bear no resemblence to her. i'm guessing she eventually found an actual boy and vivi went on to find a female black mage, although they are never mentioned in the game, which is something else i found odd.
another thing, if summoners are born with horns, imagine what that must do to their mother's lady parts when they come out??
also, are genomes able to breed? technically they are also meant to be machines, so that would be interesting to see. the product of a summoner and a genome. a little blonde child with a horn and a tail?