Well you don’t generally see horses laughing their guts out. But this case is different. Obviously something happened that is seen as laughable by both humans and equines. What could that be? Has the horse proposed to the girl, only to realize the futility of the matter? Has the girl grown a tail? Or galloped faster than the horse? Before divulging into weird thoughts, let us for a moment look at the image. They are not facing each other. Probably they are looking at something which is obviously funny. Right! They are laughing at the viewer! This is seriously funny!