ABSTRACT Play and its material-semiotic configurations are being acknowledged more and more as creative and formative forces in socio-cultural spatialization. However, subject-centered epistemologies of the roles of materiality and the thing still haunt perspectives on play. This theoretical article critically approaches and reevaluates the concept of ‘playfulness’ via affect theory in a relational ontology of play. Thinking of playfulness as a relation between bodies, things, and ideas gathered as ‘play partners’ which co-enable each other’s capacities for play evades viewing it as a causal mental state of the subject or a mere outcome of play as a practice. Rather, drawing from Lugones, playfulness can be grasped as a differential, pre-individual type of spatializing affect which is primary to play. Finally, thinking with the recent series How to Build a Sex Room, the theoretical account links to a reading of the agency of playful things in the real-and-imagined spaces of sex, kink and BDSM.