Acting is uniquely human. There is no theatre of chimpanzees, or drama for reptiles. But acting is not a monolithic skill. There are a large number of cognitive, social and emotional skills that are recruited and required in order to act. While some of these skills may be uniquely human and some are shared with other species, all evolved from animal origins. In this chapter, I explore a variety of developing psychological capabilities and their associations with the skills necessary to act and perform theatrical works. I briefly discuss how each skill develops both ontogenetically (i.e., during the child’s lifespan) and phylogenically (i.e., how it developed through evolutionary means and what purpose it serves). I also examine whether these skills are increased by affiliation or exposure to engaging in theatre. Finally, I propose a coordinated framework of what it takes, cognitively and emotionally, to be an actor, and how each of these achievements is built upon (or not) in development. My goal is breadth, not depth. Any single skill discussed in this chapter is the topic of extensive research in psychology. Some skills also have large research histories on their connections to play, pretend, imagination, drama and theatre. But as theatre is a complex, intricate, human, cultural endeavour, so is developmental psychology. Matching semantic terms and descriptions is a first step to creating a dialogue between the two fields.