Many examples of engineering go unnoticed because they are so much a part of our daily lives that we rarely give them much thought. When you decorate your house with holiday lights, you probably do not think about the engineering that was needed to produce them. This article provides a short history of holiday lights, examines how current flowing through a bimetallic strip causes lights to blink on and off, and includes the 5E inquiry lesson: Making a switch from a bimetallic strip to create a blinking bulb.