Back to the Future Part III Ending Explained
For such a memorable cinematic friendship, it’s odd that nowhere in the “Back to the Future” trilogy do we learn how Doc and Marty met in the first place. There are some obvious questions about how they got so close despite obvious differences in age, lifestyle and general interests. But after the events of the films, there are several more specific paradox-related questions about what exactly Doc knows when he “first” meets Marty.
In 1995, Doc has now sent Marty into a DeLorean time machine twice in a row, and in the process learned an absurd amount of detail about his own future. He knows he will one day invent time travel, he knows how to avoid his own death in 1985, and he also knows all about Marty’s future for the next few decades.
Since Doc isn’t the shrewdest operator, how will he play it all off when he meets the ’80s Marty? Will he just pretend he doesn’t remember anything for the duration of their friendship, or will he do a lot of drugs in the 60s and forget most of it? By the logic of the movies themselves, Doc and Marty are truly “friends in time”, as their relationship itself is a chicken-and-egg paradox.