7. Where Are The Alternative Versions Of Doc, Marty And Jennifer In The Alternative 1985?
At the end of Part One Marty arrives back in 1985 to see his slightly younger self set off in the time machine which started his adventure in the past. In Part Two the Doc and Jennifer even interact with other versions of themselves. These scenes clearly establish that two versions of the same person can coexist in the same time period. What's less clear is whether upon entering into an alternative reality you replace the existence of the other version of yourself that was there already. Even though every version of the future the characters return to is technically an alternative timeline, we'll just examine the 'bad 1985' as its the only reality they acknowledge as being an alternative reality. In the bad reality its said that Doc has been committed and that Marty has been sent away by Biff to study in Europe. They never establish where the bad reality version of Jennifer is supposed to be when she is left on the porch outside what we can assume in this version of time is not her house. What isn't clear is whether another version of the Doc was sat in a mental institution, or whether another Marty was still studying in Europe. However long the Doc had been committed for it didn't change the fact that his dog Einstein was still at his home, and other then his dog bed being upturned not looking too worse for wear. You have to feel bad for the version of Marty that was happily studying abroad as you can be sure the rich Biff would give him hell upon his return to the US!