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 wonders if the Washington, Lincoln and Custer he has encountered are from his Earth or the parallel-Earth, since all three relate histories that are markedly different from their Earth-1 counterparts, but ultimately decides the answer is unknowable.
