My mind is constantly asking this question about everything. What if dogs could talk? What if I had wings? What if marshmallows are sentient?
Many times, my brain answers the question simply and moves on. Lots of stories have addressed talking dogs. If I had wings, I would fly. Sentient marshmallows is rather... disturbing. May need to think about this some more, or not.
Sometimes when I think about a What if question, a story is born. For example, Alpha Coder started with the question, What if werewolves worked at a software company?
Once a story kicks around enough in my head, it needs to be let out. Usually I park ideas in a list. When one gets to the top, I write it.