Back to the Future Pt. III
Fortunately Pt. III in and of itself deals with relatively little in the way of time travel (because my brain is starting to bleed out of my ears). With the Delorian damaged upon Martys arrival its essentially more of a journey through Hill Valley before the West was won. Thats not to say that no further copies are made though. When Marty Prime manages to get the DeLorian jump-started using the steam power of a locomotive hes finally sent back to his original 1985 (or at least the good one, restructured after George McFly walloped Biff in Pt. I and then again from a different perspective in Pt. II). Youll probably remember that Doc chooses to stay with his newfound love Clara Clayton and doesnt actually leave 1885. But with Marty Prime making the jump through time, he invariably leaves another copy of himself Marty IX - in the distant past ending his run with 8 versions of himself including the Prime copy, that have been peppered throughout past, present and future. You might think were done there, but not quite. When Marty arrives back to the present, its only a moment before the Delorian is destroyed by, ironically, a locomotive, having come to rest on the same track in 1985 that was incomplete in 1885. However in a further twist of sweet irony, Doc. Brown appears in the same spot a little later in a new time machine that hes built into a train, presumably using parts from the Hover Board (which Marty Prime left behind, I checked). The thing is, this train is filled with his new family, Clara, Jules and Verne and theres really no way to tell how many times theyve travelled and indeed how many copies of them are out there threatening to split the fabric of time in two so unfortunately this is where the equation becomes impossible to track.
Final Total: 8 Martys, at least 8 Docs, 3 Jennifers, 2 Biffs, at least 2 Clara, Jules and Vernes and only Christ knows how many more.
If this article has proven one thing, its that the Time/Space continuum in the Back to the Future franchise is nowhere near as fragile as the Doc. repeatedly insists it is; if it were, surely overpopulating it with potentially infinite copies of the same people would surely break it, right?
I guess it's an unanswerable question but I personally Thank God that time travel hasnt been invented and that it's theoretically impossible; if it weren't we'd have all most likely been erased from existence by now. And then who would there be left to poke holes in movie concepts? No one, that's who...