The categories that define people on the move must be understood as unstable, contingent, and provisional processes. This paper contributes to a growing body of scholarship that explores the lived complexities of migrant categorization and their social implications. Based on fieldwork in Brazil and Central America, the paper investigates the processual character of categorization by intertwining temporal and spatial dimensions, focusing on specific events to understand the occasions, circumstances, and intentions that bring about adapted or entirely new categories. An eventful notion of categorization demonstrates not only how categories come into being but also how categories remain connected to particular events that are recognized or produced in response to movement. These categories stick to the identity of a subject in transit, confirming and solidifying it; however, they can also challenge the subject’s legal stability, generating new insecurities and (im-)mobilities.