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
Adventures of Captain Marvel most popular superhero, and they agreed. Director William Witney, however, was skeptical about trying to adapt Captain Marvel after the problems encountered with Superman. In spite of this, "Adventures of Captain Marvel" became the first superhero film adaptation of a comic book character. National attempted legal action to prevent Republic from developing their arch rival's most successful character, citing Republic's failure at adapting a Superman serial. Their attempt was unsuccessful, however, and Captain Marvel went into production. Writing in his autobiography of the period, William Witney revealed that in his court deposition he had claimed that both Superman and Captain