Arnold is a NeS Hero who joined the group after a genetic mishap left him with fox-like attributes. The scientist, Orë, made a careless mistake after Arnold asked him to splice his dead friend's DNA into his own, and used a fox sample instead. Orë wanted rid of this mistake and took him on a short mission to Sanctuary where misdeeds to get Arnold killed were thwarted and Arnold wound up joining the NeS Heroes instead, who offered to help him find a cure. Arnold is friendly and soft-hearted, but he has a sarcastic streak to his sense of humour. Since he met Orë, he took one of the jet packs they used to reach Antarctica from Arnold's hometown in the U.S.A..