Captain Marvel (DC Comics) 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". Fawcett ceased publishing Captain Marvel-related comics in 1953, partly because of a copyright infringement suit from DC Comics, alleging that Captain Marvel was a copy of Superman. In 1972, DC licensed the
Captain Marvel (DC Comics) "The World's Mightiest Mortal", starting with "Shazam!" #15 (December 1974). As all subsequent toys and other merchandise featuring the character have also been required to use the "Shazam!" label with little to no mention of the name "Captain Marvel", the title became so linked to Captain Marvel that many people took to identifying the character as "Shazam" instead of "Captain Marvel". The "Shazam!" comic series began with "Shazam!" #1 (Feb. 1973). It contained both new stories and reprints from the 1940s and 1950s. Dennis O'Neil was the primary writer of the book. His role was later taken over by writers