When people inevitably need to make decisions about their computer-security posture, they rely on their mental models of threats and potential targets. Research has demonstrated that these mental models, which are often incomplete or incorrect, are informed in part by fictional portrayals in television and film. Inspired by prior research in public health demonstrating that efforts to ensure accuracy in the portrayal of medical situations has had an overall positive effect on public medical knowledge, we explore the relationship between computer security and fictional television and film. We report on a semi-structured interview study (n=19) investigating what users have learned about computer security from mass media and how they evaluate what is and is not realistic within fictional portrayals. In addition to confirming prior findings that television and film shape users’ mental models of security, we identify specific misconceptions that appear to align directly with common fictional tropes. We identify specific proxies that people use to evaluate realism and examine how they influence these misconceptions. We conclude with recommendations for security researchers as well as creators of fictional media when considering how to improve people’s understanding of computer-security concepts and behaviors.