Here is how this works:
The point is to ask a "What if" question (i.e. how would the story be affected if an event had happened differently than it did). Each poster must answer the "What If" posted previously and provide a new one so the thread keeps going. The only rule is that the "What If" posted must have had a significant impact on the story.
So let me start with this:
What if Robb executed Jaime Lannister?