When the time came for this sprawling sci-fi mystery about airplane-crash survivors stranded on a mystical island to cough up the answers to its countless questions, Lost largely balked. But as frustrating as that was (we still don't know who shot at the outrigger — maybe it was the missing Russian from The Sopranos?), the series finale committed a far worse crime: It revealed that the "flash-sideways" storyline, in which the main characters lived in an alternate world where they'd never crashed on the Island, was some kind of corny new-age afterlife. In other words, half of what the audience had spent the final episodes watching literally never happened. "We have to go back!" may have been the series' most famous catchphrase, but this short-sighted decision makes the series hard to happily revisit.