Batman (comic book) work, and first interior-story work, appeared in "Batman" #19 (Oct.-Nov. 1943), for which he drew the cover and the first three Batman stories, and penciled the fourth Batman story, inked by Norm Fallon. Like all Batman artists of the time, Sprang went uncredited as a ghost artist for Kane. Villains which debuted during this early era included the Mad Hatter in issue #49 (October 1948) and Killer Moth in issue #63 (February 1951). In 1953, Sheldon Moldoff became another one of the primary Batman ghost artists who, along with Win Mortimer and Dick Sprang, drew stories credited to Bob Kane,
Jan (comic book writer) down in 1985, Jan, together with many other comic book writers, had to do work for other editorial companies. Jan published his first (and only) erotic comic 'Laszivia' in Norma Editorial, and created characters such as 'Cab Halloloco' and 'Los ultimos de Villapiñas' for the Jauja comic magazine. The character 'Superioribus', drawn for the editorial Forum, is also a superhero parody. In 1987, Ediciones B began publishing a Superlopez magazine. In this way Jan can continue working on this character till now, with a few other contributions from time to time to other magazines, such as the characters "Pum Tarrota"