Nick and Sally are trying to guess what animal is the toughest one - is it a lion? Oh no, it must be the enormous elephant! Why not at all, says The Cat. The toughest of all is a teeny tiny Waterbear. Huh? Off to meet Cat's friend Wally the Waterbear. After shrinking down in the Thingamajigger, they find Wally and start to play the Tough Enough game! Wally is tough enough to live anywhere, so it's off to Freeze Your Knees Snowland to test it out. Then they go to the super hot Gritchity-Gratch Desert, then even a trip into space! Wally can live anywhere! He really is the toughest of all!