I would like to propose a more expansive use of the term "ninja."
We all know what ninjas are, those black-clad masters of secrecy, possessors of near superhuman skills in the martial arts and stealth. They can appear to vanish into thin air, catch a throwing star with their bare hands, jump over towering castle walls, or even enter a trance-like state indistinguishable from death so as to deceive their enemies.
But there are other people who are also very good at things, possessors of near superhuman skills in their own particular domains, those who excel at making coffee, shopping for groceries, Scrabble, etc. Aren't they in some sense ninja-ish? Should they be denied the "ninja" appellation? I think not.
Let us henceforth refer to the "classic" ninja as a ninja-ninja. Those who are very good at something else will be whatever-else-they-are-very-good-at-ninjas: a spelling-ninja, a crossword-puzzle-ninja, a boiling-spaghetti-ninja, a tying-shoes-ninja, a detecting-grammatical-errors-in-the-sentences-of-others-ninja, a Dewey-Decimal-System-ninja, a nose-whistling-ninja, and so on. This morning I was a sleeping-in-ninja, deflecting the metaphorical "throwing stars" of my children's shrieks with my "bare hands" of extreme slumber.
What kind of ninja are you?