Narrative worlds often include features that would be implausible in the real world: Characters remain eternally youthful carpets can fly. For my dissertation, I conducted five experiments that demonstrated how the accessibility of knowledge specific to particular fictional worlds affects readers' comprehension of plausible and implausible events. In Experiment 1, participants were faster to read events that fit within narrative worlds (e.g., bullets bouncing off Superman's chest), even when those events were implausible in the real world. In Experiment 2, participants read about familiar characters experiencing events that were either highly plausible (e.g., Superman shooting lasers from his eyes), mildly implausible (e.g., Superman hypnotizing a criminal with his eyes), or very implausible (e.g., Superman turning a criminal to stone). Participants read the highly plausible events fastest. There were no significant differences in reading times between the mildly and very implausible events. The stories in Experiment 3 described ordinary characters (e.g., a bank teller) in realistic or fantastic worlds (e.g., Metropolis) experiencing realistic events (e.g., being killed by bullets) or implausible events (e.g., bullets bouncing off their chest). Participants were consistently slower to read about ordinary people experiencing implausible events, even within the context of fantasy worlds. In Experiment 4, participants read about ordinary characters, unfamiliar fantastic characters (e.g., a native of Krypton), or familiar fantastic characters (e.g., Superman) experiencing implausible events. Participants were slowest to read sentences containing an ordinary character, and there were no differences in reading times for sentences with the familiar and unfamiliar fantastic characters. In Experiment 5 participants read about the same characters from Experiment 4 experiencing realistic events. Participants were fastest for the unfamiliar ordinary characters, and equally slow for the familiar and unfamiliar fantastic characters. Taken together, these studies clarify how readers use their real-world knowledge, prior knowledge about a particular fictional world, and textual cues to assess the plausibility of events in narratives.