Every important story plot must be set up ahead of time. First, this item must be highlighted somehow to make it memorable although initially it may seem trivial. Second, it needs to be repeated somehow so we don’t forget it. Third, it needs to payoff somehow so we realize why it was important in the first place.
In “The Revenant,” there’s a setup involving a young man’s canteen. The first time we see this canteen, he’s scratching a design on the front and annoying the villain, who tells him to stop it. This seems to show the villain’s nastiness, but it serves the dual purpose of also setting up the canteen as something important although we don’t know it at the time.
When the villain buries the hero alive, the young man tosses his canteen, with the design scrawled on the front, on the hero’s body to give him water. This seems to show the young boy’s compassion that he’s not as cold-hearted as the villain, but it also reminds us a second time about the importance of the canteen.
The third time we see the canteen is when the hero accidentally drops it while stealing a horse from some French soldiers. When the English-speaking soldiers capture a French soldier who had that canteen, everyone realizes that the hero didn’t die after all but must have survived. This causes the villain to flee the fort.
Setting up story elements is crucial because without proper setups, story twists seem to come out of nowhere, which creates an unsatisfying story known as deus ex machina. This refers to the old Greek tragedies when the hero would find himself in a bind and the gods would come out of the sky and save the hero while defeating the villain. This would be like the hero in “Die Hard” fighting the terrorists through the whole movie only to win in the end when Godzilla pops out of nowhere and eats the villain.
In “WALL-E,” the fire extinguisher is setup initially when WALL-E scavenges different junk from the garbage and finds a fire extinguisher. Not knowing what it is, he trips it and it sprays all over the place. This appears to be nothing more than another example of WALL-E looking for valuable junk to save.
Later on when WALL-E is trapped in the escape pod, there’s a fire extinguisher attached to the wall. As WALL-E struggles to get out of the escape pod before it can explode, the fire extinguisher appears right next to him. When the escape pod blows up, WALL-E is seen floating through space, using the fire extinguisher like the thrust of a rocket to guide him.
Think of any scene where something major happens and you must make sure you properly setup the details of that major scene earlier. Make the initial appearance of that item memorable somehow, then subtly remind us of its existence a second or even a third time. Then payoff the importance of that detail to show how it twists the plot around in a major scene somehow.
Watch bad movies and one reason why they’re so bad is because they don’t setup details properly. Think of “Jaws 4” where the shark suddenly appears in the Bahamas to chase after a single family. How did the shark know the family had moved to the Bahamas? To see how bad “Jaws 4” bungles the idea of setups, watch this YouTube video of comedian Richard Jeni ripping apart the movie.