Introduction: a hyperlinked past: theorizing retroactive continuity -- A brief prehistory of retroactive continuity -- High society: historical revisionism in justice society comics -- Crisis control: crisis on infinite earths and the creation of a unified comic book universe -- Moving images, moving history: retroactive continuity in television and film -- Putting it all together: retroactive parody and play -- Citation needed: Wikipedia and the mutability of the past -- Conclusion: playing the retcon game.