This chapter uses Possible Worlds Theory to analyse how the spectator responds to the complex collaborative experience provoked by Uninvited Guests' production Make Better Please. It proposes that this philosophical framework facilitates a new way of considering the spectator's creative input and generative response to the participatory performance event. Examining how Possible Worlds Theory is used by digital theorists to elucidate the processes of hypertext fiction, Swift argues that the theory provides tools and a language which also recognise and validate the operations of participation in performance. This new application of Possible Worlds Theory makes an important contribution to the consideration of the immersive and interactive experience of the active spectator.