One of Us is Lying critiques stereotyping and gossip by highlighting how corrosive they can be for both the individual and community. Both stereotyping and gossip can be dehumanizing and prevent people from seeing each other as whole and complex. Further, they are hypocritical. Stereotyping denies the reality that people are complex and contradictory, as evidenced in Bronwyn being both a high achiever but also incapable of excelling at chemistry and Addy being both pretty and insecure. Gossip is hypocritical because anyone is capable of making mistakes, as the book demonstrates with each of the narrators, their families, and their friends. Significantly, the book emphasizes that gossip is characterized not by whether information is accurate but whether that information is shared for the entertainment of non-interested parties.

Simon cultivates both stereotyping and gossip through his app, About That, and his stereotyping extends even to himself. When he refers to himself as the “omniscient narrator,” he is referring to his status as social outsider. An omniscient narrator is typically an unseen narrative voice that reports events, as Simon does through About That. His gossip is intended to humiliate others and make them feel small, the way that Simon feels.