World War Z is just the latest pop-culture incarnation of the Zombie Apocalypse. Adam Frank says the zombies keep coming because they're trying to tell us something. MPC/Paramount Pictures hide caption

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That's a meme: President Obama and gymnast McKayla Maroney struck her "McKayla is not impressed" pose when members of the Olympics team visited the White House in November. Pete Souza/The White House/Getty Images hide caption

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Spraying the Declaration of Independence (John Trumbull's "Declaration of Independence"). hide caption

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