Los Angeles Herald, first doing spot illustrations and later sports cartoons. He moved to New York in 1934 to become a sports cartoonist for the New York World-Telegram, where he created the infamous "Brooklyn Bum" character that became synonymous with the Brooklyn Dodgers. He also worked for The saturday Evening Post, Time, and Life. Comics historian Maurice Horn stated that "Mullin's love of his craft and of his subjects shone through in all of his cartoons: under the surface roughness lurked a strong undercurrent of affection and optimism." He greatly defined the modern sports cartoon, now a dying art form, by combining representative portraiture, cartooning, and editorial commentary.