Cat in the Hat Knows a Lot About That! - Season 3

When Sally destroys Nick's model of a mountain, the Cat takes them to meet Sara of Serendip, an inventor who helps them understand that you can make new discoveries through your mistakes. (involves mixing colours and making a volcano) / Nick discovers that Sally can't hear him when he yells from his bedroom window if their bedroom windows are closed. The Cat takes them to the Soundy Sea and they learn that sound travels in waves.

Sally loses her slidiness and when they go to the Frictionarium, they find out that there's a force called friction that can stop a person from sliding. / The kids want to get a trunk up into the treehouse and go to the Machine-a-Ma-Zoo where they're introduced to some simple machines, but learn about the pulley.

Nick unintentionally loses Sally's bouncy ball They go to Ballaballo and learn how different balls are made of different materials that make them bouncier. / Nick and Sally are having a sleepover in the treehouse and Nick is startled by a shadow. The Cat explains that shadows aren't scary if you know what they are. He takes them to Shadowland where they learn about how the position of the light can make shadows grow or shrink.

Nick and Sally are in the treehouse making funny faces at themselves in the mirror when they notice a bird flying back and forth into the tree branches. They discover that the bird is building a nest and they want to get a closer look but can't do it without disturbing the birds. The Cat takes them to a mirror world where they learn how reflections work and they concoct a kind of periscope that allows them to watch the bird without disturbing it. / Nick gets some new train cars for his train set and wants to add them to his train, but the magnets won't connect. The Cat takes them to a magical magnets world where they learn how poles attract or repel.

Nick is trying to learn how to ride his bike and in Balencia, he discovers the things to keep in mind when you're trying to maintain your balance. / Nick and Sally need a strong piece of string to pull their train, but it breaks, and they don't have anything stronger in their craft box. The Cat takes them away, but the TMJ malfunctions and they have to make an unscheduled landing. It turns out they've shrunken and are inside the craft box, where they discover that they can create a stronger string by braiding several strands together.