MakeBelieve is a story-generation agent that uses common-sense knowledge to interactively compose short fictional texts with a user. A user starts a story, and MakeBelieve attempts to continue it by freely imagining possible sequences of events for the character the user has chosen. The agent uses "common sense" about causality and how the world works, mined from the Open Mind Common Sense corpus, and combines this with very simple lingustic techniques for story generation to produce pithy but interesting stories. MakeBelieve also uses common sense to evaluate a story it has written to catch logically inconsistent and incoherent events and actions.