John tends to be a bit of a goof, making bad jokes and using off-beat and subtle irony to make humor. John has a typical nerd nature in that he is very passive, and he follows commands more easily than the others, complying with commands not because of their logical sense but because the command told him to. He is more prone to stupid ideas than his friends and is made out to be the butt of a lot of jokes with his chats to them through Pesterchum. John's inner nature drifts toward an overall good guy, more out of necessity to avoid his father than because of moral obligations. He even celebrates the birthdays of his friends, Rose, Dave, and Jade.
While not the most intelligent or imaginative of the main characters, John is by far the most inventive - from the beginning, he shows more innovative prowess in combining items than any of the others, even before the introduction of the alchemiter; he demonstrates this with his poster-nailing and harlequin-funniness-amplifying abilities.