We are developing software tools for authoring real-time applications involving virtual actors. The actors have mood, presence and personality. They follow a script, using body language and gesture to convey an interactive story that has been scripted beforehand by an author. Scripts can contain random elements, so the same story is never told twice. As the story unfolds, end-users participate and become part of the story by controlling an actor, by interacting with actors, or by giving instructions to the story telling system. For example, as two actors are embroiled in an argument, a user might instruct his actor to leave the room, or to end the argument by conceding. The virtual actors adapt as changes in the story occur, using guidelines from their scripts to decide how to respond and behave. In this video, we present the history of our research in Improvisational Animation and discuss some of the principles involved in creating animated virtual actors who perform autonomously in real time and how this can be applied to the creation of compelling interactive experiences which allow for endless possibilities, yet always conform to the framework established by author and animator.