This paper explores the interplay between structured urban planningUrbanplanning and the unpredictability of informalityInformality in urban developmentUrbandevelopment. At its core, it examines how cities, exemplified by Naples, evolve through informal, superfetative processes that stem from a grassroots level, contributing to their adaptability, resilience, and vibrancy. By challenging conventional planning paradigms, superfetationSuperfetation embodies a collective urban creativityCreativity that redefines urban landscapesUrbanlandscapes in response to changing community needs and environmental conditions. The discourse is framed within the theoretical context of systems theory and biological paradigms, advocating for a planning methodology that can embrace flexibility and adaptability. This approach reflects the principles of autopoiesisAutopoiesis in biology, where systems are self-creating and continuously evolving. The paper argues that cities can be interpreted as Complex Adaptive SystemsComplex Adaptive Systems (CAS) (CAS), where informality plays a crucial role in fostering a symbiotic relationship between urban environmentsUrbanenvironments and their inhabitants’ individual experiences, needs, and creative solutions. The paper presents case studiesCase studies from Naples, specifically focusing on the practices of superfetation within this complex and rich urban settings. These examples demonstrate how informal architectural practices, while often at odds with legal frameworks, provide essential contributions to the city’s architectural and social fabric. The study suggests that such practices should not only be tolerated but actively integrated into the planning paradigm to enhance urban resilienceUrbanresilience and adaptability. In conclusion, the paper calls for a re-evaluation of urban governanceGovernance and planning regulations to acknowledge and incorporate the value of informal processes. It proposes a shift towards more inclusive planning frameworks that accommodate the fluidity of urban lifeUrbanlife and recognize the contributions of all citizens to the urban designUrbandesign process. This approach would not only enhance the vitality of cities but also ensure they are better equipped to respond to future challenges. The insights gained underscore the need for further research into the integration of informal practices within formal planning to maintain their essence and vitality in urban development.