Peter Sullivan is a fictional character from the movie "Margin Call," which explores the early stages of the 2008 financial crisis. He is portrayed as a junior risk analyst at a large investment bank, where he uncovers critical information about the company's precarious financial situation. His character represents the moral dilemmas faced by individuals in the finance industry during times of crisis. In the film, Peter's discovery leads to a series of high-stakes decisions made by the bank's executives. His role highlights the impact of corporate culture and the ethical challenges that arise in the world of finance and investment banking.