Arnold appeared in films as an actor opposite the comic duo Martin and Lewis, and also wrote the screenplay for the Martin and Lewis vehicle "The Caddy" (1953). In 1956, Arnold started writing for such television series as "The Tennessee Ernie Ford Show" and "The Rosemary Clooney Show". In the 1960s, he began writing and producing episodes for such sitcoms as "The Real McCoys," "Bewitched", and "That Girl." Regarding "Bewitched", which he produced for its first season, Arnold noted, "With this show, I saw a great opportunity to accomplish something. Fantasy can always be a jumping-off place for more sophisticated work."