http://scribblenauts.com/Nintendo Power had an article about this game for the DS. A very basic way to describe it would be solving puzzles using anything you can think of, similar to madlibs. Say you're in a desert with a thirsty person; you could write soda and one would appear that the man could drink, You could solve the same puzzle with, rain cloud, oasis, coffee shop, watermelon might even do it, etc.
The developers spent most of the time just going through dictionaries looking for words to add to the list! According to the developers anything that's not, copyrighted, A pronoun (though Einstein is in there for some reason), oddly specific (like blue angry dog would materialize a dog but, it probably won't be blue), or above the E 10 rating, it's in there.
The title screen acts as a free area where you have no goal and can just experiment. Some of the videos I’ve seen include God vs. the Kraken.