Spoilers below.
Going to bring up two interesting theories; the first is about Rey's Parenting and the second is about Snoke.
The first came from an article I read claiming that Obi-Wan could be Rey's father. It was an interesting theory but to me seemed less likely than Luke being her father. The theory was that in the gray area between III and IV Obi-Wan had a girlfriend on Tatooine (this actually happened in an Expanded Universe book), and they had Rey but the mother, was forced to abandon her on Jakku. Seems far fetched nut equally interesting. I have also read some that make Han the father, of course making Kylo and Rey siblings.
As for Snoke, I just want to add that his theme music in The Force Awakens, and the music playing when Palpy is talking about him in Revenge of the Sith, are nearly identical and might actually be the same song... I'm not sure.
Here is my source: