The kid had swallowed a coin and it got stuck in his throat, and so his mother ran out in the street yelling for help. A man passing by took the boy by his shoulders and hit him with a few strong strokes on the back, and so he coughed the coin out.
"I don't know how to thank you, doc..." his mother started.
"I'm not a doctor," the man replied, "I'm from the IRS."
