12 Fiendishly Clever Comic Book Movie In-Jokes You Probably Missed

4. Keep Calm & Call Batman

Man Of Steel is surprisingly crammed with comic book Easter Eggs and in-jokes, as we've already established with Snyder's self-referential 300 in-joke, and the best of all isn't one of the many Lex-Corp logos, or even the obscure and very clever Blaze Comics reference, it is instead a tongue-in-cheek homage to Superman's greatest DC rival, Batman.

In a surprisingly prescient nod to the sequel announcement that will team Ben Affleck's Batman up with Henry Cavill's Superman, there's a poster in the background of the climactic battle between Supes and Zod that carries the immortal line "Keep Calm And Call Batman."

Director Snyder apparently had no idea about the jokey Egg, as he spoke after the release to confirm its presence and source:

"When Zod's tearing the building apart with his heat vision, there's a Be Calm And Call Batman sign on the wall there, just really small... You might even have to stop the movie to see it but it's definitely in there. That's a Double Negative Productions . D Neg is the visual effects company here in London that worked on all the Dark Knight movies, and they definitely did that. And , I was like, 'That's awesome.'"

There's also a nod back to the Watchmen movie in Man Of Steel, as eagle-eyed comic book fans stopped a familiar looking blood-stained smiley face in the background of one Superman shot...