In the time between Back to the Future and Back to the Future: Part II, the role of Marty McFly’s girlfriend had been recast, putting Elisabeth Shue in the part. The scene from the end of Back to the Future was reshot, and the result is the beginning of Back to the Future: Part II. Here they are, compared.
Without Twitter, we would have never known that time travel has been made possible. Not only is it possible, but as you can clearly see from this picture, it’s been tested successfully. I cannot even begin to imagine all the things we can do now; all the mistakes that can be fixed. This is a great day for science, a great day for mankind.