3. How Can You Change The Future If You Plan To Live In The Past? - Back to the Future (1985)/Back to the Future Part II (1989)
The Plot Twist: Attempting to see if a series like
Back to the Future holds up to close scrutiny is something of an exercise in futility, given that the movies embrace their goofy, time travel mechanics with a knowing self-awareness. Still, one has to question the "twist" that takes place at the end of the first movie and carries straight into the plot of the second, given that it gives rise to one of the most downright illogical moments of the entire series. One might argue that this isn't a "twist" in the traditional sense, but you might still count it as one - a "semi-twist," if you will. You'll remember, then, during the last scene of the original
Back to the Future - and having returned to the present in the arms of his loving girlfriend Jennifer - Marty McFly's zany friend Doc Emmet L. Brown returns from the future, exclaiming that there's
something that needs to be done about the couple's children. We never find out what this is, but it's a funny way to the end the movie, implying that their will be more adventures.
But, Uh... Consider this for a moment: Doc Brown returns from the past and tells Marty and Jennifer that they need to travel to the future to prevent a situation in their future. At first, we accept this, because a scientist is proposing the plan, and who are we to question the laws of time travel? This plan is eventually carried out, the rights are wronged, and Marty's kids - we presume - turn out fine. Well, they would have, had Doc's plan made any sense. Think about it: Doc only needed to
tell Marty and Jennifer that, in 2015, they needed to ensure that something was done about their kids. Going to the future and changing events there accomplishes nothing, because everybody plans on coming back to the present. If you live in the present, what does it matter if the future gets changed, given that you don't live there, and it hasn't happened yet? You'll only have to repeat the process again when you catch up to it, because anything you changed hasn't happened - only
past events can alter the future. Hence, Doc's plan is a complete waste of time. For the guy who built a working time machine, he sure is dumb.