One paradox raised by this film that has never been satisfactorily answered (at least, as far as I am concerned) is: what happened to Marty II?

Here's the breakdown, and for God's sake don't read this if you haven't seen the movie!

  1. Marty McFly (henceforth referred to as Marty I) travels back in time to the 1950s, where
  2. He changes the past, which
  3. Unbeknownst to Marty I, alters the future. Then, he
  4. Goes Back To The Future where he witnesses...
  5. Marty McFly (henceforth referred to as Marty II) traveling back in time to the 1950s.

All well and good, you say, everything's come full circle. But no! Because Marty I is in a DIFFERENT WORLD than he was at the beginning, a world created by his tampering with the past! The Marty he witnesses leaving had a completely different life than Marty I did - he is not the same person.

So where does he go?

The problem is compounded by the events of the second movie, where Marty I goes back to the 1950s again and watches himself doing stuff from the first movie. We assume it's him and not Marty II, because Marty II would probably react in a completely different manner than Marty I did to the same situations, having grown up in a happy home with well-adjusted and successful parents. (Nature vs. nurture, anyone?) So wherever Marty II went, it ain't here. Maybe the controls were set to some different era? And he certainly doesn't return to his own timeline because Marty I is already there enjoying the hell out of his stolen life.

At this point my head starts to spin. Maybe Marty II just dies or something. Poor Marty II.

UPDATE 6/3/2000: Someone suggested to me that the changes Marty made did not take effect in the present until after Marty went into the past - so there was no Marty II. The chronology then is, Marty reappears in the present, sees himself going back in time, and then a chronal wave sweeps over everything and transforms it into The World Where Marty's Life Is Great. Sounds good to me.