They've got over 1,000 positive reviews!
Promising review: "These slippers are amazing! I live in the basement with hard floors (tile, wood, anything but carpet), and the floor is super cold. It's like living on an iceberg, and no matter how many layers of socks I wore, my feet were still cold. I have a condition called Raynaud's where my hands and feet have trouble staying warm and turn blue and purple because there isn't enough blood flow to keep them warm, so I practically always have cold feet, and they often go completely numb from being so cold. I put these slippers on, and within about two minutes, my feet were warm. The feeling came back into them, and I could not feel the cold floor at all. For practically the first time ever, I'm going through winter with warm feet! These slippers are incredibly comfortable, fit my feet exactly, and they are completely adorable to boot! I loved these so much that my mom and sister got some as well! My mom got sheep, and my sister got penguins. All of us love these miracle slippers. I HIGHLY recommend them! They are the best slippers I've ever owned, and I've owned a lot." —Random chick
Get them from Amazon for $24.99+ (available in six sizes and in 48 animals).