Yellow Kryptonite
From superman.nu: Supermanica
Yellow Kryptonite
A Synthetic Kryptonite created by Lex Luthor as a hoax to mentally torture Superman. Luthor claimed to have a machine capable of creating hovering Kryptonite globes of various colors, including the previously unknown yellow variety. All the globes were in fact fakes, though they managed to successfully fool one of Superman's Superman Robots who at the time was called Superman Robot-in-Training (Act No. 277, Jun 1961: "The Conquest of Superman!").
