Dogs may have their day, but when it comes to the internet, it's a cat's world. A YouTube video of a cat "playing" the keyboard has netted nearly 47 million views, and the sourpuss kitty known as "Grumpy Cat" sparked such an online sensation that Friskies made her its Official Spokescat, paying for her personal assistant, and chauffeur. But what makes the ordinary house cat extraordinary? We talk with two authors about cats' behavior and development, and why we're so obsessed with them. What have you always wanted to know about cats?