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Sedated bear falling out of tree

After wandering onto the University of Colorado campus in Boulder and being tranquilized, this black bear fell out of a tree to a soft landing on safety mat below. While the image will live on, unfortunately the bear wasn't so lucky: It was hit by a car after being released back into the wild. (@cuindependent/Twitter)

2012 Year in Review: Most viral photos

From the Harper wedding photobomb to the most retweeted photo ever, this slideshow takes a look at the most viral photos from 2012.