Once relegated to cinema or history lectures, bank runs have become a modern phenomenon that captures the interest of students. In this article, the authors explain a simple classroom experiment based on the Diamond-Dybvig model (1983) to demonstrate how a bank run--a seemingly irrational event--can occur rationally. They then present possible topics for discussion including various ways to prevent bank runs and moral hazard. (Contains 2 figures, 4 tables, and 10 notes.)