The Big Bang Theory Soft Kitty Keychain If you love all things adorable soft kitty, then this is the key chain is for you! The Big Bang Theory Soft Kitty Key Chain features the one thing that will calm down Dr. Sheldon Cooper - the super cute soft kitty - on a soft key chain. You'll be reminded of the hilarious antics from The Big Bang Theory protagonist Dr. Sheldon Cooper every time that you unlock the door! Measures about 2 1/2-inches long.