A dad walks into the market with his ten-year-old son. The kid is spinning a 25-cent piece in the air and catching it between his teeth. As they walk through the market someone bumps into the boy at just the wrong moment and the coin goes straight into his mouth and lodges in his throat. He immediately starts choking and going blue in the face and Dad starts panicking, shouting and screaming for help.

A middle-aged, fairly unnoticeable man in a gray suit is sitting at a coffee bar in the market reading his newspaper and sipping a cup of coffee. At the sound of the commotion he looks up, puts his coffee cup down on the saucer, neatly folds his newspaper and places it on the counter. He gets up from his seat and makes his unhurried way across the market. Reaching the boy (who is still standing, but only just) the man carefully takes hold of the kid's balls and squeezes gently but firmly.

After a few seconds the boy convulses violently and coughs up the 25-cent piece, which the man catches in his free hand. Releasing the boy, the man pockets the coin and walks back to his seat in the coffee bar without saying a word.

As soon as he is sure that his son has suffered no lasting ill effects, the father rushes over to the man and starts effusively thanking him. The man looks embarrassed and brushes off the father's thanks. As he's about to leave, the father asks one last question "I've never seen anybody do anything like that before - it was fantastic, what are you, a surgeon or something like that?" 

"Oh, good heavens no" the man replies. "I work for Revenue Canada".