The Tractors are characters in Cars.
Tractors are hard workers. They enjoy what they do, plowing through the fields on a nice warm day, and then falling asleep under the moonlight. But every so often they wake up to the sound of snorting and giggling trailing off into the distance, and they find themselves lying on their backs staring up at the stars. But they don't mind. It's actually kind of nice to get to sleep lying down for a change.