The Adventures of Superman (radio) home planet of Krypton is located on the far side of the sun, as opposed to a distant star system as it is in most stories. During the journey to Earth, baby Kal-el grows into an adult and emerges fully grown from his ship after it lands on Earth. He is never adopted by the Kents but immediately begins his superhero career. This was eventually retconned in later episodes to match the narrative of the comic books. This serial introduced the fictional mineral kryptonite, the radiation from which can weaken and even (in some continuities) kill Superman. Aside from giving
Superman: Secret Origin an enemy. Superman leaves anyway, and Sam orders the Army to attack. The soldiers do little to Superman, but John, in the Metallo suit, manages to weaken him by exposing him to the kryptonite. Ricocheting bullets hit the kryptonite, which explodes and injures John and allows Superman to escape. Sam and his troops arrive at the "Daily Planet", and orders it shut down until they can get definitive answers about Superman. Lex takes John into surgery and replaces his heart with a kryptonite generator, turning him into Metallo. Sam reveals to Lois, Perry, and the "Daily Planet" staff that Superman