People often engage in self-repetition-repeating the same story, joke, or presentation across different audiences. While behaving consistently has generally been found to enhance perceptions of authenticity, 10 studies demonstrate that performers who are revealed to be self-repeating are perceived as less authentic. We find convergent evidence that this effect is driven by observers' implicit assumption that social interactions are unique. Self-repetitions violate this assumption, leading observers to judge performers as inauthentic because they are thought to be falsely presenting their performance as unique when it is not. We demonstrate this effect across multiple contexts (politics, entrepreneurship, tour guiding, and comedy), finding that observer awareness of self-repetition decreases perceived authenticity even in situations in which it is normative to repeat a performance and in which repetition is required. The decrease in authenticity is eliminated only when performers overtly acknowledge self-repetition, as performers are no longer viewed as falsely presenting themselves. Moreover, performers who fail to acknowledge their self-repetition are penalized similarly to those who explicitly lie that the performance is unique-an unacknowledged self-repetition is thus seen as a lie by omission. Finally, we recorded repeated job interview responses and found that observers who were unaware of the self-repetition could not discern tangible differences between unrepeated and repeated responses. However, when observers believed that they were viewing a self-repetition, they judged the interviewees as less authentic. Together, our findings provide insight into how people assess the authenticity of self-presentational behaviors and the implicit assumptions that influence social judgments. (PsycINFO Database Record (c) 2019 APA, all rights reserved).