10 Astonishing Facts About Kryptonite
9. Superman Didn't Know He Was An Alien Until He Discovered Kryptonite
The first comic book to debut Kryptonite was the 1949 story, Superman Returns to Krypton. The title character encounters a con man called Daniel Rivers who pretends to be a psychic called Swami Riva. As Superman tries to stop him, the fortune teller claims he will place a hex on the superhero. Although Riva has no superpowers, Superman is left so weak, the con-artist knocks him out with a single punch. Since he was able to incapacitate the world's strongest superhero, Riva believes he has astral abilities.
Supes eventually figures out that the stone in Riva's turban is responsible for him losing his strength. He travels back in time to find the origin of the stone, only to learn it is a chunk of his home planet, Krypton. It is in this moment when Superman learns he is an alien.
It's also worth mentioning that Kryptonite resembles a red crystallised substance in its first appearance in comics. Kryptonite didn’t take on its iconic glowing green appearance until Action Comics #161 in 1951.