Batman
The first Batman story, "The Case of the Chemical Syndicate", was published in "Detective Comics" #27 (May 1939). Finger said, "Batman was originally written in the style of the pulps", and this influence was evident with Batman showing little remorse over killing or maiming criminals. Batman proved a hit character, and he received his own solo title in 1940 while continuing to star in "Detective Comics". By that time, Detective Comics was the top-selling and most influential publisher in the industry; Batman and the company's other major hero, Superman, were the cornerstones of the company's success. The two characters were featured side-by-side as the stars of "World's Finest Comics", which was originally titled "World's Best Comics" when it debuted in fall 1940. Creators including Jerry Robinson and Dick Sprang also worked on the strips during this period.
Superman (comic book)
Due to the Superman character's popularity after his premiere in "Action Comics" #1, National Allied Publications decided to launch an entirely new magazine featuring a single character, which at that time was unprecedented. "Superman" #1 appeared on the shelves in the summer of 1939. Superman now also had the distinction of being the first ever hero-character featured in more than one comic magazine. By issue #7, Superman was being hailed on the covers as the "World's Greatest Adventure Strip Character". Perry White, a supporting character who had originated on the Superman radio program was introduced into the comic book in issue #7 (October 1940). Editor Mort Weisinger began his long association with the title with issue #11 (July–August 1941). Jimmy Olsen first appeared as a named character in the story "Superman versus The Archer" in "Superman" #13 (Nov.–Dec. 1941). In the early 1940s, "Superman" was selling over a million copies per month. By 1942, artist Wayne Boring, who had previously been one of Shuster's assistants, had become a major artist on Superman. "Superman" #23 (July–August 1943) featured the first Superman comic book story written by someone other than Jerry Siegel. The story "America's Secret Weapon!" was written by Don Cameron despite bearing Siegel's signature. Siegel introduced Mister Mxyzptlk in issue #30 (September 1944). A more detailed origin story for Superman was presented in issue #53 (July 1948) to mark the character's tenth anniversary. Another part of the Superman mythos which had originated on the radio program made its way into the comic books when kryptonite was featured in a story by Bill Finger and Al Plastino.