This paper uses clinical material to illustrate how play between child and analyst can be mutative when a joint play space is co-created. When children are in play mode, they are in an altered ego state that is more fluid, more flexible, and more creative than their ordinary state. Children do not simply use play as a way to tell their stories. They also experiment, improvise, and try out new ways of being and making meaning between themselves and others. During shared play states, child and analyst co-create a new, lived experience, which can be re-organized and re-integrated into a different narrative about the child and his world. The author believes that these ideas have application to therapeutic action in adult analysis as well.