Little Lemmings - It's cold outside, but Nick and Sally want to keep playing. Is there a way to stay warm out in the cold? Cat's friend Lars the Lemming will know! He lives in the Wundra-Bundra-Tundra. It's cold out, but with Lars' fur coat, he doesn't even notice! They help Lars find a new home, one where there's more food for him and his family and they discover that he uses the snow to help keep him warm! Back at home the kids wear two winter coats to help them keep warm. But what's even warmer than that, hot chocolate! Keep the Beat - Nick and Sally have been running around the backyard and now their chests are thumpity thumping! The Cat explains that that is their hearts boom boom booming! But why? wonders Sally. A visit to Dr. Giggles will answer that question. By shrinking down super small, they follow Dr. Giggles' directions to follow the path that blood takes, learning about how the heart is a pump. They watch Thing 2's heart beat faster when he runs, and slows down when he stops. With all this running around, their bodies are now making another sound - rumbling tummies!