adversary, was introduced. Superman's first alien villain, Brainiac, debuted in Action Comics #242 (July 1958). The monstrous Doomsday, introduced in Superman: The Man of Steel #17–18 (Nov.-Dec. 1992), was the first villain to evidently kill Superman in physical combat without exploiting Superman's critical weaknesses such as kryptonite and magic. Alternative depictions The details Superman's story and supporting cast vary across his large body of fiction released since 1938, but most versions conform to the basic template described above. A few stories feature radically altered versions of Superman. An example is the graphic novel Superman: Red Son, which depicts a communist Superman who rules the Soviet Union. DC Comics has on some occasions published crossover stories where different versions of Superman interact with each other using the plot device of parallel universes. For instance, in the 1960s, the Superman of "Earth-One" would occasionally feature in stories alongside the Superman of "Earth-Two", the latter of whom resembled Superman as he was portrayed in the 1940s. DC Comics has not developed a consistent and universal system to classify all versions of Superman. Cultural impact and legacy The superhero archetype Superman is often thought of as the first superhero. This point can be debated: Ogon Bat, the Phantom, Zorro, and Mandrake the Magician arguably fit the definition of the superhero yet predate Superman. Nevertheless, Superman popularized this kind of character and established the conventions: a costume, a codename, extraordinary abilities, and an altruistic mission. Superman's success in 1938 begat a wave of imitations, which include Batman, Captain America, and Captain Marvel. This flourishing is today referred to as America's Golden Age of Comic Books, which lasted from 1938 to about 1950. The Golden Age ended when American superhero book sales declined, leading to the cancellation of many characters; but Superman was one of the few superhero franchises that survived this decline, and his sustained popularity into the late 1950s led to a revival in the Silver Age of Comic Books, when characters such as Spider-Man, Iron Man, and The X-Men were created. After World War 2, American superhero fiction entered Japanese culture. Astro Boy, first published in 1952, was inspired by Mighty Mouse, which in turn was a parody of Superman. The Superman animated shorts from the 1940s were first broadcast on Japanese television in 1955, and they were followed in 1956 by the TV show Adventures of Superman starring George Reeves. These shows