Over the years,Superman and his secret identity Clark Kent have made both official and unofficial cameos in the Marvel Comics universe. However, the DC Comics hero's best secret cameo is one that most people missed, as the Man of Steel made a hidden cameo in The Death of Captain Marvel: The Graphic Novel. While it's not the easiest to see, Superman's kiss curl, cape, and part of his costume can be seen hiding behind a group of mourning Marvel heroes.
Marvel Comics and DC Comics have crossed over before, as Superman, Wonder Woman, and The Flash were among the heroes who battled against their rival publisher's heroes in DC vs. Marvel by Ron Marz, Peter David, Dan Jurgens, and Claudio Castellini. However, the best official crossover is, without question, JLA/Avengers by Kurt Busiek and George Perez, as each of Earth's Mightiest Heroes fought to save their universe from cosmic destruction. Unofficially, Superman and Clark Kent have made many cameos, whether it's Clark Kent showing up at the Daily Bugle or Marvel teasing the hero is worthy of Mjolnir. However, his best and arguably most secret unofficial cameo came after Captain Marvel's death.
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InThe Death of Captain Marvel: The Graphic Novel by Jim Starlin, Steve Oliff, and Jim Novak, Captain Marvel's death reunite the greatest heroes in the Marvel Comics universe as they pay tribute to their fallen friend. In a group shot featuring everyone from Iron Man, Hulk, Starfox, and Spider-Man, Superman can be seen in the background, making a secret cameo that's easy to miss. On the final page, Superman (and his kiss-curl) can be seen standing behind Wolverine, as part of his suit, boots, and cape are
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