That's a great question. To be honest, we use PEI stories to break the ice with candidates and understand how he/she thinks, communicates and how interesting his personality is.
Answering your question, it was a girl, who went to Peru to fight poverty and educate people.
On the one hand, I met people, who have great experience, but have pure communication and presentation. Unfortunatley, they fail. On the other hand, it is worth mentioning that everyone may have a story with little impact and make me feel interested.
It depends on the presentation: some people invent stories to show their best. And if they rehearsed enough, they could get it.
My suggestion to you is make your PEI stories such entertaining that people want more after you finish them.
All the best,