Me: "So, now that we've defined this fallacy, let me give you some examples. (noticing that a student in the front row is doodling) Jay, this is not the time to be drawing."
Jay: "But it's fun!"
Me: (with a joyful excitement that I'm sure confused Jay) "Um, I can't really come up with any example that's better than that!"
Jay and classmates: " . . . "