I was in a high school humanities course, and the philosophy instructor was talking about the “essence” of things. For example, he said that a clock which stopped telling time could no longer be considered a clock, because the telling of time is the “essence” of clockness.
After giving a few more examples he plucked an empty paper cup from his desk, ripped out the bottom, and held it aloft. “What about this?” he asked the class. “Is this still a cup? I would say not.”
To which I replied, “I’m sorry, but I just don’t think your argument holds water.”
Pretty much the pinnacle of my career as a smartass.