Spinach vs. Parsley
Nowhere on earth is as mysterious as the produce section of your local grocery store. It's the one place where people will voluntarily admit ignorance and not feel bad about it. You'll often see men (and women too, let's be fair) wandering around with a glazed and pained look on their face as they consult a list and try to figure out what green thing might possibly correspond to this mysterious word on the shopping list.

I was in the produce section today when I was stopped by a man who pointed hopefully at the bundle of cilantro I was carrying and asked "is that spinach?" No, sir, it is not spinach, I explained. But I pointed to the spinach, whereupon he thanked me and wandered over to where I had pointed and picked up the parsley that was next to the spinach. "That's not spinach," I explained. "That's parsley. This is the spinach." And, so saying, I picked up a bunch of spinach to show the difference. He thanked me. Then he pointed to my cilantro one ore and asked "is that parsley?"