You can understand the plot without the first sequence, but remove it and you lose more than just 10 minutes of run time. Even changing a single shot can alter

You can understand the plot without the first sequence, but remove it and you lose more than just 10 minutes of run time. Even changing a single shot can alter how an audience engages with a movie farther into its runtime. One example I remember is from Jaws. Spielberg explained that changing the editing of an earlier scare (when they explore the abandoned boat) made the audience much less shocked at the first reveal of the shark later on. The change was literally the timing of a couple of shots; less than a second at most. The first 10 minutes of Up colours the entire rest of the film.