30 MPH: Tie those sneakers tight! We're going to run with some of the fastest animals on the planet. From the cheetah to the horse*we'll discover what it takes to travel over 30 mph. The Biggest and the Fastest: Why are polar bears so big and cheetahs so fast? Great question! We'll show you how different animals use their incredible size or lighting speed to survive. Something Extra: Some animals just have something extra. A horn! a third leg! a special ability! We've used our great minds to uncover the secrets of these extraordinary creatures.