Mental representations of unknown others play a central role in person perception. These representations, informed by our memories as well as the affective associations we acquire though our past experiences, heavily influence how we perceive, evaluate, and react to new people we encounter in our day-to-day lives. Three papers aim to understand the antecedents and consequences of these representations at different stages of relationship formation and functioning-from evaluating unknown others to getting acquainted with these individuals. The first paper focused on idiosyncratic cues pertaining to representations of significant others and showed that women evaluated unknown men who resembled their partner (vs. those who did not) more favorably, even when they were not consciously aware of the idiosyncratic cue. In everyday person perception, such idiosyncratic cues are encountered simultaneously with cues shared across perceivers. The second paper provided the first systematic examination of how resemblance to known others (an idiosyncratic cue) and facial width-to-height ratio (a shared cue) simultaneously influence person perception. Shared and idiosyncratic cues had additive effects when participants made evaluative judgments (i.e., snap judgments of liking). Across three studies, facial width-to-height ratio was negatively related to liking. However, this association was significantly attenuated for women with a wide-faced romantic partner. The idiosyncratic cue predicted liking only when novel faces resembled newly encountered people who engaged in blameworthy behaviors or when they resembled significant others. Shared and idiosyncratic cues interacted to influence processing efficiency when participants made categorical judgments (i.e., indicated whether unknown faces resembled someone they knew). Participants made slower and less accurate responses to wider faces resembling a liked known other (vs. not). By focusing on static photographs of faces, these studies showed that shared and idiosyncratic cues profoundly influence person perception. The third paper complements this research by showing that likeability judgments from photographs predicted likeability judgments following live interactions, even when judgments were separated by two weeks and when interactions provided more opportunities to learn about the person. Drawing from theorizing on mental representations, the present research sheds light on the multitude of factors that influence everyday person perception from photographs to live interactions.