Nintendo has loosened its grasp on its characters for the Wii launch, with its characters appearing in a number of third-party games. Scribblenauts Unlimited is yet another Wii U game to get Nintendo cameos, as evidenced by these Mario and Zelda characters.
The announcement was scant on details about which words will work, but it does promise "dozens" of characters and items will appear. It also promises unique behaviors for some of the characters, which will likely play off the existing behaviors for various other character types. We can hope this means Scribblenauts Unlimited will finally answer the question: could Bowser wielding the Master Sword beat Cthulu? We've been thinking about that one for years.