The silver lining to the dark cloud of breaking a bone is obviously the sweet cast you get to wear. It tells the world that you're a badass (or very clumsy, but let's stick with badass). But how can you make casts even cooler? By making them look like an X-ray of your broken bone!
That's just what Casttoos are. You send them in your X-ray, and they'll send you back a waterproof "cast tattoo" that will make it look like you can see right through your cast. So cool it almost makes me want to go break my arm. Almost.