Haha. That's pretty awesome. (And cute. :3) The couple of people I know named Craig are from my Dad's generation. Actually one of my closest friends is called Brandon. And it's almost impossible to not know a Ben.
It's not so much memorising it, just knowing how your starting, where the plot is going, what the climax is going to be and how you'll end it. Man, I've done some horrible, rushed endings to narratives in my time.
Just gotta hope you can easily relate it back to the picture or sentence or whatever it is that you're given. I do the same thing though. Otherwise I'd spend my two hours of exam just trying to think of an idea.