The book Green Eggs and Ham was written by Dr. Seuss as part of a bet with a publisher that he couldn't write a book only 50 words. (Seuss won.) When animals sleep through a cold period it's called hibernation, but when animals sleep through a hot period it's called estivation. Pope Gregory IX was apparently a dog person, because he tried to exterminate all cats from Europe. Nearly one tenth of all men alive today in central Asia are descended from Mongolian Emperor Genghis Khan, who clearly got around. Around 39% of humans have an extra small bone behind their knee called a fabella. Caterpillars liquefy in their cocoons before turning into butterflies.