But What If They Really Exist?

The concept of parallel universes gets very confusing very quickly; take a look at the Many Worlds Theory. But you don't have to go down that rabbit hole to understand the layman's explanation. 

If parallel universes exist, there could be an unlimited number of you and me "living" somewhat to very different lives in them based on the choices we've made and not made.

Possibly the best movie interpretation of this is Back to the Future I, II, and III. What could be more that than Marty McFly encountering himself, family, and friends, in the past, present, and future?

Just as Katelyn Tarver does in a video of the same name.