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.