3. With All Changes Made In 1955 and 1885, How Come Jennifer Was Still On The Swing Outside Her House?
When Marty, Doc and Jennifer returned to 1985 in Part Two they discovered the world as they knew it had changed, and they were now in an alternative version of 1985. To put things back as they were Doc and Marty went back to 1955 to stop old Biffs influence from drastically changing the future. They themselves did make some more changes to time they hadnt originally happened when Marty had accidentally gone back in time in Part One. For example Biffs friends got knocked out with sandbags, Biff crashed his car into another manure truck and one shop owner had sold an extra pair of binoculars. These may not be the biggest changes of time, but its hard to discuss time travel without mentioning the butterfly effect. Surely any of these changes would have made had big implications on the time period they left Jennifer in. But thats not all. After successfully stopping Biff become a millionaire Doc Brown is inadvertently sent back to 1885 creating another new version of events. Marty then learns that the Doc is killed in the past so goes back to rescue him, which would create another new timeline of events. The changes here are even more dramatic as an entire century of ripples through time would occur before Marty rejoined Jennifer in 1985. So...after three major changes to the past how on earth was Jennifer still asleep on the same porch bench where Marty had left her?