Miley Cyrus has added yet another dog to her growing menagerie. His name is Happy, and because of Miley, his story has a happy ending. Miley tweeted a photo of herself getting her hair washed while clutching the adorable black-and-beige pup, and wrote, "He was left in a box in front of Walmart. I don't understand how people can be so cruel. That's why we named him Happy." As for what kind of dog he is, Cyrus writes, "We're not 100% [sure] the breed we think Rottweiler Beagle mix :)." According to People magazine, Happy joins Miley's other pooches Ziggy, Lila and Floyd. The magazine reports that Cyrus' boyfriend Liam Hemsworth was seen Tuesday purchasing bags of pet food and a dog bed for the new arrival.