When many people think of pigs they think of mud and slop, or else bacon and bacon. But there's so much more to love about these rotund creatures, and that's precisely why sisters Ellen Stanley and Mary Lynne Rave started National Pig Day in 1972. Did you know that the reason pigs roll around in the mud is to cool themselves off since they do not sweat? Or that pigs place fourth on the animal intelligence list? Perhaps pigs aren't just for dinner; they also make for charming dinner guests.