"Catsomization" is a fancy word for customization of your feline driver. Choose from variety of fancy costumes and hats to make your cat look stylish!
To open catsomization, tap on your garage and then on "Tap to edit" above your cat's character.
Drag the costume or a hat to your character and it will be saved automatically.

Some costumes are available at the beginning of the game, while others require you to pass a certain stage to unlock them. Once the costume is unlocked, you can purchase it for either gems or gold.