A ferret played a crucial role in building our National Accelerator Laboratory. There’s a crab that comes with its own pompons. There are 11,000 species of bats. When hyenas laugh, it doesn’t mean anything funny. The difference between kangaroos and wallabies will surprise you. This week’s mental_floss List Show gives us a quick rundown of things you don’t really need to know about animals, but you’ll want to, because they are quite interesting.