On August 16, 2001, a crop formation appeared overnight in front of the Chilbolton Radio Observatory in England. It was a clear response to the Arecibo Message which was sent into space by Carl Sagan and Nasa in 1974.
It seems impossible that people could have made such large and complex formations so perfectly in the dark of one night. On top of that, scientific analysis of the crops showed that they had not been pushed down with blunt force as you would expect in a man-made design. Rather, the bottom nodes of the stalks had been heated via some form of focused radiation so that they wilted over and strangely, came to rest at a 90 degree angle.
Most people will have a skeptical reaction to their appearance, as it so closely resembles the typical "grey" alien depicted in so many movies. But it is worth noting: That image was not the product of Hollywood's imagination. Just like the "flying saucer", the description originally came from people who claimed to have seen them first hand. Hollywood took that description and sensationalized it for their own purposes.