20 Most Unforgettable Viral Videos of 2013
Air-drumming grandmas, singing spacemen, twerk fails, and, of course, Ylvis

Peter Kramer/NBC/NBC NewsWire via Getty Images
From Norwegian lunacy to out of this world (literally) musicianship, brilliant parodies to mind-bending stunts, 2013 offered a treasury of viral videos — and a whole lot of twerking. Here, we revisit the year's best widely seen and shared clips. So get ready to laugh, cry, cringe, and wonder if some of these people have too much time on their hands. BY DAN REILLY