Computer simulations are widely used in physics instruction because they can aid student visualization of abstract concepts, they can provide multiple representations of concepts (graphical, trajectories, charts), they can approximate real-world examples, and they can engage students interactively, all of which can enhance student understanding of physics concepts. For these reasons, we create and use simulations to teach physics, but we also want students to recognize that the simulations are only as good as the physics behind them, so we have developed a series of simulations that are intentionally incorrect, where the task is for students to find and correct the errors.