Throughout the 1950s on the Earth of his home universe, Captain Thunder battled all manner of crimes and injustices across the globe, becoming that world's greatest hero. His greatest battles were against a coalition of incredible creatures known as the Monster League of Evil, whom he fought across 1,953 different dimensions and finally imprisoned in a misty purgatory-like realm. As Captain Thunder was leaving to return to his native dimension, the Monster Leaguers placed a curse on the Captain that would cause him to turn evil when next he assumed his heroic guise. Through some unknown mishap, Captain Thunder (in his Willie Fawcett identity) wound up in and alley of Metropolis on mainstream Earth in 1974. When Willie witnessed a crime in progress, he transformed himself into Captain Thunder with the intent of capturing the criminals, but instead turned to evil as the Monster League had planned. Captain Thunder fought two titanic battles against Superman (proving himself to be a peer to the Man of Steel in sheer might), after which the confused hero was forced by the Action Ace to use his wisdom to break the curse that the Monster League placed on him. Realizing that he was in the wrong dimension, Captain Thunder thanked Superman for his help and used the power of his magic word to return to his native universe (S No. 276, June 1974: "Make Way for Captain Thunder!").
Author's Note: Captain Thunder was obviously based on Captain Marvel of SHAZAM fame, who appeared in comic books published by Fawcett Publications from 1939 to 1953. "Captain Thunder" was originally supposed to be Captain Marvel's official name, but it was changed at the last moment. Even though DC Comics began publishing the adventures of SHAZAM in late 1972, the decision was still made to have Superman battle a derivative character so as not to interfere with the planned All-New Collector's Edition publication Superman vs. Shazam (No. C-58), which was published two years later.