John Smith is of average height, average weight, average economic background, and is, as far as any doctor can tell, completely normal. He hasn't been exposed to mutating substances, has no mystical ties, doesn't have access to unusual technology, and hasn't had any unusual training.
Regardless of all of his complete and utter normalcy, John's history is filled with events that defy astronomical odds. He has won the lottery 7 times, been struck by lightning twice with no ill effects, survived a 2,000 foot drop from a mid-air plane collision with only minor bruises, and once typed the first page of Hamlet by repeatedly banging his head against his keyboard in frustration.
John Smith is a living statistical abberation.
He is the Improbable Man.