The Cat in the Hat Knows a Lot About That! Season 2 Episode 11 - Little Lemmings - Keep The Beat >Nick and Sally have been running around the backyard and now their chests are thumping along! The Cat explains that this is their hearts 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!