Arnold is the owner of Arnold's Drive-In. He is a short, tan-skinned man with a grey mustache. He can do karate, dance and speak Korean, Chinese, Japanese and English. His mother was Chinese and his father was Japanese. Arnold and Fonzie are good friends. Richie Cunningham, Warren "Potsie" Weber and Ralph Malph often complain that the food is bad/the place is dirty, but they don't really mean it and they are good friends with him. Arnold never cleans the place, he has a boy named Daniel come in once a week to clean everything including his car, under the pretence he is teaching him karate. He often complains about how certain behavior among the teens who frequent Arnold's (particularly Johnny) or sometimes the adults might make him lose money. Arnold also writes replies on the bathroom wall to the graffiti the kids wrote.
Arnold got married in season 3 and leaves the restaurant to Al Delvecchio. Since Al got married in season 10, Arnold bought back his restaurant and it is unknown what happened to his wife. He and Fonzie are partners and help him out running the restaurant.