Canadian militia leader James Fitzgibbon literally stumbles onto 2 American raiders outside a taven. I quote now:
...one of them levelled a rifle at him. The brash Fitzgibbon extended a hand to the American and moved toward him in a friendly manner, as if he had recognized him as an acquaintance. This action confused the American for just long enough to allow Fitzgibbon to seize the rifle and order him to surrender.
Americans befuddled by Canadian friendliness? Suburbia might refer to this as our petard.