BeTheActor is an collaborative performance where the performers play together with the digital audience characters as well as the interactive digital stage environments. Audience collaborates with performers to overcome the task of the scene and continue the performance. It transforms the aesthetic of performance into an interactive and collaborative experience. Compared to previous work, our system enables a collaborative performance among the real performers, virtual audience characters, and the stage environments. We developed various techniques to realize performative collaboration such as digital audience characters, participatory scene effects and real-time word balloon. Using processing and computer vision, the facial image of the audience is mapped on the digital performers. The system is described and analyzed based on results from testing the performance in a theater, and in a user study with 40 performers.