The Brush Realm is a location from Epic Mickey 2: The Power of Two. It is where the Paintbrush is located. Mickey has to paint in the rocks to make a pathway to the other side where he can warp out using a magic mirror. And if he falls, don't worry; the rocks will catch him. Mickey can also Paint in Thinned stars and they will shoot across the sky. The challenge "When You Wish Upon a Star" can be done here.
In Fantasia, when Mickey falls asleep, he dreams that he is on a clifftop using the powers of the magic hat to control the cosmos and the forces of nature. This level is based off that with the option to paint in stars and comets taking the place of the magic hat.