Harley is a conniving character with little to no regard for anybody but himself and his Pokémon. He tends to get personal vendettas against people for the smallest of reasons. His vendetta against May began when she said she had never heard of Cacturne before, Cacturne was "scary" and that his cookies were "not half bad"; however, the supposed "real" reason he started to dislike her was because she looks just like a classmate who stole his last snack when he was a small child. He keeps photos of people that he has grudges against in a notebook/photo album. He also tends to inflict humiliation to try to get the better of an opponent, showing sadistic pleasure when he does. This is evident when he pretended to be friends with Max in order to get him to tell an embarrassing story about May only to record it and play it during a Contest. Finally as evidenced by his contest performances, Harley shows no qualms in using dirty tactics to win.