!! Carl and Ellie's life vs. Muntz's life
In ''Up'', the whole montage serves as an interesting {{Deconstruction}} of the GoalInLife and ManicPixieDreamGirl tropes. The opening scene before the montage sets it up like the two ''might actually go to Paradise Falls''. But then, life gets in the way. Carl and Ellie live a long, happy life in a nice neighborhood. Paradise Falls, exotic and distant but seemingly achievable, falls by the wayside. When Carl finally thinks about it, both he and Ellie are retired. So he buys some tickets to South America -- possibly as a consolation -- but they never even go. Just as his thoughts turn towards Paradise Falls, Ellie passes away. Then the neighborhood, excepting the house Carl and Ellie built, gets razed. Carl's guilt over the whole thing and lack of a source of happiness turns him into a bitter old man with a TragicDream, and plenty of time to think about WhatCouldHaveBeen. Meanwhile, everything recognizable around him gets destroyed, he keeps his house identical to the way it was when he and Ellie finished it -- even keeping the chairs. Then, after his trial, he is faced with a choice -- leave behind everything for a retirement home, or cling desperately to his memories of Ellie. He TakesAThirdOption and goes off to redeem MyGreatestFailure.

Muntz, by comparison, serves as a ShadowArchetype for Carl, insanely and single-mindedly searching for the bird, which serves as his own MyGreatestFailure and causes him to become paranoid. In an interesting twist, Muntz even ''exploits'' Carl by using the same things that drive him when he sets fire to Carl's house. Going further, Muntz is completely forgotten by modern society and has completely passed the point of going home to his life as a respected former hero, which ironically seals him in a loop; the ''only'' way to receive recognition in the world and be reinstated into the (probably defunct) Explorer's Society anymore is to find that bird. And the only reason that he's in the loop? He preferred faking success to simply coasting on his other victories (look in Ellie's ''Spirit of Adventure'' and a newspaper reads something along the lines of "Muntz breaks altitude record"). Muntz's stubborn refusal to let things go leads to his dying in the place he spent most of his life in as a forgotten, dusty relic.