Captain Marvel, also known as Shazam, is a fictional superhero appearing in American comic books published by DC Comics. Artist C. C. Beck and writer Bill Parker created the character in 1939. Captain Marvel first appeared in Whiz Comics #2 (February 1940), published by Fawcett Comics. He is the alter ego of Billy Batson, a boy who, by speaking the magic word "Shazam", can transform himself into a costumed adult with the powers of superhuman strength, speed, flight, and other abilities. Based on book sales, the character was the most popular superhero of the 1940s, outselling even Superman. Fawcett expanded the franchise to include other "Marvels", primarily Marvel Family associates Mary Marvel and Captain Marvel Jr., who can harness Billy's powers as well. Captain Marvel was also the first comic book superhero to be adapted into film, in a 1941 Republic Pictures serial titled Adventures of Captain Marvel.