Cat on a Diet

To get this achievement you will have to find all of the secret costumes in a total of 80 levels. To find a costume you will have to click on a crack that can be hidden in the background of some levels. A textbox will appear when you are in a level with a costume in it "I sense a costume hidden somewhere around here..." is what it will say.

You will have to unlock all the Dimension X bonus levels to get this achievement as there are costumes hidden in those levels as well. This means that you have to get 3 stars on all levels (except the last X dimension level) to get this achievement.

I hope this guide helped you get one step closer to 100%!