FAT Question or Skinny Question?

We have a rule in our classroom. When in Literature Circles, one must ask FAT questions. "What is a FAT question?" you ask? Well, it is a question that requires thoughtful, more drawn out responses. Where as a skinny question might be answered with only one or two words.
I have a poster in my room with a fat cat and a skinny cat on it. We look at the poster often and say "Is this question a FAT question or a Skinny question? How can we make it fatter?" The kids love it, because they take ownership of their questions!