Open The Door, Earthman!
A man is wandering through the woods when he encounters two aliens. The aliens are standing before two scarlet boxes. One box is completely empty. The other holds a death ray. The aliens issue an ultimatum to the man. Open the right box, and the Earth will be spared an invasion. Open the wrong box, and the aliens will conquer the world. The man is given five minutes to make his decision. The man frantically attempts to determine which box is the empty one. He taps on them, but they both sound hollow. He lifts them, but they both weigh the same. He moves towards each box, as if to open it, to gage the aliens' reaction, but their expressions never change. With the clock running down, the man finally selects the box on the right. It is empty. Taking the aliens' words literally has solved the riddle. The aliens depart to play their horrendous "game" on some other world.