Crossovers between manga and American comics are few and far in between. While Marvel Comics has dabbled in manga-inspired creations before (most notably, its series of Marvel Mangaverse comics), it looks like the publisher is planning to go even further down the rabbit hole. Marvel's C.B. Cebulski revealed on Twitter that a crossover is planned between Marvel Comics and Hajime Isayama's "Attack on Titan." Pitched as, "What if the titans from Hajime Isayama's 'Attack on Titan' attacked the Marvel Universe," Cebulski confirmed that the project is "not a joke" and that the crossover will drop in two weeks in Japan.

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Not a joke, folks. Attack on Titan and the @Marvel universe are crossing over! In 2 weeks. In Japan. Want a teaser? pic.twitter.com/9AF5fqWLfX- C.B. Cebulski (@CBCebulski) November 3, 2014

Set in a post-apocalyptic world where humanity was nearly wiped out by giant creatures called Titans, "Attack on Titan" follows Eren Yeager, a young man who enlists in the military with his friends after a Titan devours his mother. The series, currently ongoing, details his adventures in the army as he discovers his ability to transform into a Titan.

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It's understandable why Cebulski had to clarify that the crossover wasn't a joke. Not only is it unprecedented, the reveal also comes amidst a massive amount of mysterious Marvel event teasers that reference past events for the publisher, including a crossover between "Age of Ultron" and "Marvel Zombies." However, the Marvel Universe/"Attack on Titan" crossover is clearly happening, whereas the mystery teasers are more than likely a tease for Jonathan Hickman and Esad Ribic's "Secret Wars" event.