The Castle of Illusion has fallen into Epic Mickey's "Wasteland," Dreamrift creative director Peter Ong explained to me during a meeting at E3. "Mickey's quest actually takes place in the Castle of Illusion in this game, but at the same time it's situated in Wasteland, so you'll see characters familiar to Epic Mickey and Wasteland such as Oswald being involved in Mickey's quest," Ong said.
However, the Castle has changed, as castles tend to do when video game series are named after them. Mizrabel is constantly casting illusions on the castle, justifying the alterations mandated by the game design. This is used to very cool effect: not only do parts of the castle resemble environments from other Disney media (like a Peter Pan-themed nautical level), you see the illusion begin to take hold as you navigate the castle. Rooms will be part castle, part ship, with "illusion" seeping in.
Dreamrift games tend to include interactivity between the top and bottom screens – like feeding your monster pal on the bottom screen of Monster Tale to power up his attacks on the top screen. Epic Mickey also uses the dual-screen design, to allow you to paint and thin objects in the environment. Certain objects will appear in outline form on the bottom screen, for you to paint (or apply thinner to, where appropriate). This is a minigame in which you have to trace precisely, in order to bring that object up on the top screen, thus creating a platform or other necessary item. You'll even unlock "sketches" that you keep in your inventory, in order to place (and draw) anywhere you want. In the demo, this was a Thwomp-like object bearing Pete's face.
You can get additional bonuses – and in general interact with the Disney world more – by fulfilling quests for the Disney characters you rescue, all of whom hang out in rooms in a "safe" area of the castle. For example, Rapunzel asked me for a comb, which I found by asking the Beast.
"When we first sit down to think of our new idea, we don't think, 'Oh, it's going to be a dual-screen-intensive game.'" Ong said. "But then as we talk through our ideas, there's always some new way to use the second screen that we can't not do. It's just an interesting question for us to explore." For Epic Mickey, the screen allows players to participate in the creation of Disney-style art, which seems like a good fit.