Chekhov's Gun
Showing an object or detail early on that becomes important later. The idea is that nothing gets screen time unless the story is going to use it.
How this film uses it
Robert Zemeckis and Bob Gale's script is a masterclass in setup and payoff. The DeLorean, the clock tower, the 88mph requirement, the photograph and Marty's guitar playing are all introduced casually. Later, each one comes back as something the plot needs, so nothing is wasted.
Where to see it
The lightning-strike sequence. Every setup from the first hour pays off at the same time.

















