For me it was right at the beginning. They said it was a dungeon game. It would describe a room, etc, and I would take some action. But I thought that this dungeon was built in some intricate database. But then I told it that I wanted to leave, got to an inn, where I flirted with the bar waitress, and soon we were watching the sunset in some meadow. As cheesy as that was, it was then that I went "oh shit" this is a machine that can respond to language with language in a way that simulated actual understanding and intelligence, concepts and schema, and everything else, and I knew then that the world would never be the same again. People here talk about the crazy things they solved with AI, and I get that...but the first time I actually talked to a machine and didn't feel like it was either random gibberish or scripted, but dynamic and responsive. The first alien I ever met, and he knew my language.