The discovery of the planet Neptune is presented as a case study for adding some useful history and philosophy of science to the science education curriculum. The discovery of Neptune is a great story in its own right, with quirky characters, missed opportunities, and a dramatic climax. But there are also some valuable insights to be gained about the scientific process. The events leading to the discovery of Neptune highlight the logic and limitations in testing a scientific hypothesis. They also show ways in which scientific observations can be influenced by the scientist's theoretical presuppositions.