Building on a fourfold conceptual framework—in which space is discussed in “four acts” through the notions of affordance, relational space, spatial knowledge, and spatial pedagogization—as well as on previously gathered data through case-study research, the chapter discusses the way children, in the frame of a fairly heterodox participatory design process, challenge the conceived vision of design professionals in regard to the physical alteration of public space. Evidence stemming from an ongoing public space transformation project, located on the outskirts of the city of Lima, Peru, suggests that children, by appropriating and modifying specific aspects of the intended design according to their intuitive needs and preferences, as it is being implemented, defy the “prescriptive affordance” that underpins its pedagogization—that is to say, both explicit and implicit “spatial design tactics” meant to state how public space is to be not only used, but also apprehended. Overall, it is believed that the inherently conflictual character of participatory design/planning processes becomes exponentially more puzzling due to children’s capacity to “spy with their little eye” and performatively and subversively contradict “professional decisions,” for designers are usually bad at “guessing,” tend to dislike dissension, and lack responsiveness to children’s views and attitudes.