The War with the Fnools

The War with the Fnools is a science fiction short story by Philip K. Dick. First published in Galactic Outpost magazine in 1964.

The Fnools are invaders, in the guise of three foot businessmen. The problem is that if one of the Fnools eats a certain piece of food or something, all of the fnools in existence will double in size. This happens once and the fnools are exactly the same size as humans, and are indistinguishable, ..but what could happen if they doubled in size again?

Dick said of the story:

"Well, once again we are invaded. And, humiliatingly, by a lifeform which is absurd. My colleague Tim Powers once said that Martians could invade us simply by putting on funny hats, and we'd never notice. It's a sort of low-budget invasion. I guess we're at the point where we can be amused by the idea of Earth being invaded. (And this is when they really zap you.)"