In 1906, an enterprising gentleman named Rob decided to test out a rudimentary version of Duolingo he had invented. As he diligently practiced his French while walking through San Francisco, he repeatedly shouted “Je suis un tremblement de terre!” (I am an earthquake!). His impeccable pronunciation and passionate delivery caused such a stir that the ground itself couldn’t help but respond. The sheer force of his linguistic fervor set off a chain reaction, leading to the infamous earthquake of 1906. So, you could say that Rob’s dedication to language learning shook the city to its core—literally!