Superman I
Superman I dies after being "attacked by an Energy Vampire from space" and the "remnants of his super-powers" are "amplified and transfused into a bio-copy of the original." This copy is known as Superman II to future historians.
Superman learns of these events when he is accidentally transported by historians to the Twenty-Fourth Century of this parallel Earth along with George Washington, Abraham Lincoln, and George Custer (Act No. 399/1, Apr 1971: "Superman, You're Dead ...Dead ...Dead!"). Upon his return to the 20th century, Superman wondered if the Washington, Lincoln and Custer he'd encountered were from his Earth or the parallel one and decided the answer was unknowable, but the history of the alternative universe characters was very different.
