We're going to be talking about this past weekend's episode of Game of Thrones for a long time — it was a war epic and a dramatic tour de force, filled with palpable ambition. But this isn't the first time a single episode of television has redefined what's possible in the medium.
Here are 10 single episodes of science fiction and fantasy shows that changed television forever. To help put this list together, we talked to Javier Grillo-Marxuach, creator of The Middleman and writer for some of our favorite shows. (Grillo-Marxuach has contributed to io9 before.) What follows is a synthesis of our own ideas and his.