I don't think everyone truly appreciate the level of thought and consideration that went into the film. Carl Frederickson is an old man that lived a lonely life since his wife of many decades has died and he has no children or other family members to keep him company. Carl and his wife originally bonded over a mutual love of the Adventures of Charles Muntz, an explorer who was shunned after a bird skeleton he brought back to the United States was declared a forgery. Munte was called a fraud, stripped of his membership of the organization he worked for. He promised to bring the bird back from the jungles of Paradise Falls and swore he would never return until he did. Ellie, Carl's wife, hoped the 2 of them could one day go to the Paradise Falls. Coming back to the story and the main timeline, a construction company bought most of the land around Carl's house and constantly pesters him to sell the house so that they can build on his land. After Carl injures one of the construction workers he is committed to a retirement house. However he decides to pull of the most absurd schemes of all by putting enough ballons up his chimney so that it carry his house up in the air. While the house floats over the city, Carl realizes that a boyscout named Russell who was stuck under the Porch has been inadvertently carried up with him. Not long after landing Carl and Russell both find the bird that Charles Muntz has been chasing some 70 years ago by luring him with chocolate. Carl runs the bird off and eventually end up finding out that Charles is in fact still alive after decades of staying in the jungle and obsessively looking for the bird. At first Carl is grateful to meet his hero who he presumed to be dead. but it soon becomes clear that Charles lost his mind over the years and has resorted to murdering everyone who comes to the Paradise Falls to keep them from taking the bid away from him. Carl and Russell narrowly escape Muntz while Muntez accidently jump to his doom when his foot is caught in the strings of Carl's house. When it comes to twist, there is the surprising one. It's sort of a twist to learn that Charles is even alive. The audience on the first viewing forgot that he was even a character. But still there was no reason to believe he went rogue at this point. Secondly, despite Charles Muntz not having a lot of screen time before being revealed that he was an actual villain, there were some hints towards his true intentions. First of all and more obviously, he is looking for the bird that Russell befriended and there was obviously going to have some sort of conflict around that. Secondly, Charles is presented obscured and shadow from the very start on his in person appearance in the film. So the few screentime he had was very well used. Finally there is the twist necessary for the plot to progress. Almost all the conflict is about Charles intentions so you can't really have much of a plot without him. If Charles wasn't in the movie it would have weaken the movie's overall message. Ultimatly, " Up " is a story about letting go of the past. Every single thread of this movie perfectly align with that message. Carl and Charles are not really that different. Each of them share an important trait. Outside the fact that they are both old, they both had the most important thing in the world to them taken away. For Carl, he lost his wife. He can't get over his obsession of carrying her memory with him. Ultimatly this drives him away from everyone else and leads him to an insane fixation on getting his house to Paradise Falls to fulfill his wife's dream. Charles also lost what he most carred about : his reputation. He went from being a celebrity beloved by the public to an outcast despised as a fraud. Likewise he drives everyone else away while he frantically searches for the bird in Paradise Falls unable to let go and live his life as normal.
Another thing they had in comon was that trying to fulfill their goal will certainly kill them. Carl can't take the house all the way to Paradise Falls because the house will either fall on top of him efore he gets here or he will be lost in the jungle forever as nature's obstacles keep him from his destination. Charles can't get the bird that he wants because it's in a maze that traps anyone who enter it and he literally goes to his grave trying to take it. Both Carl and Charles are the same name by the way. Carl is just the German word for Charles. They both mean free man. Because that's what they both need to do for themselves in order to keep them from taking their losses to the grave with them. Carl wears a soda cap on his shirt that Ellie gave him when they were kids to show that he carries the past in the very litteral sense. Charles does the same thing, wearing the Explorer's jacket from all the way back in the days when he was a member of Explorer Society. You can even see where the patch was ripped off. This is a fantastic way to show that audience that the characters only live in the past. But for both of them the sad truth is that when you live in the past, you live alone because everyone else has already moved on. The Paradise Falls are a metaphor for the lonely space that people are put in who can't let go off emotional pain. That way they eventually, if they let themselves being consumed by bitterness and despair to the point that no one wants to be around them anymore. One last piece of connectivity between the 2 that put things into perspective is that when Carl becomes enraged at Russell for the last time before the final confrontation, he yells at him, saying that he will take his house into the Paradise Falls even if it kills him. Carl chased a dream that was long gone. Charles is a man who wasted all of his years of life trying to get the past back to the present. But it's impossible. The film message is nearly tied up with a nice bow in that. Russell was essentially set up to potentially be another link in the Charles and Carl chain. Russell also obviously lost something important to him. There was the potential for him to end up in the same way. Ultimatly, Carl himself breaks that chain by realizing that living in the present is the only way to prevent becoming like Charles was. And see that even though the thing that he treasured most is gone, there are other things to treasure in the present. And his friendship with Russell is one of those things to be treasured in the present.
