Symbolism I've noticed in 'Up.'

*Russel was the child Ellie and Carl never had. Remember there was a part where the couple went to an obgyne and they learned Ellie wont bear a child? Then Russel came ibto Carl's life.
*Carl was the father Russel never had. Russel once told Carl of his father, whenever they ate ice cream, they would count the red and blue cars. The ending showed Carl and Russel doing that.
*Remember the toy bird on the table beside the frame? That was Kevin. Kevin is a guardian angel, i guess? Because the toy bird was always beside the frames and Kevin did a lot if saving for russel and carl.
*the things inside the house of carl symbolizes the emotional baggage that carl carries with him, when he finally gave them up that was when his house became lighter, moved on.
*the balloon that young carl owned was the blip he and russel "parked" in the end.

Carl's initial journey was a suicide mission to be with Ellis again. Seeing the house disappear, meant he was letting Ellis go, not fully, of course. Just enough so he could live life knowing the love they shared, not what they had lost in death. The house's final resting place is imperative to Carl and Ellie's relationship; they are together, even in death, but are happier ... in Paradise. When/if Carl meets Ellie again, all will come full circle.

Russell captures the innocence of a child that often holds more wisdom than adults. This can be seen when Russell goes to save Kevin, and when he says that sometimes the boring things he hates the most.

Dug captures the perpetual loyalty and goodness that humans wish they could keep forever. Nothing will taint Dug's infectious positivity. Much like Hachiko, "my master WILL come back! All I need do is wait!" Dug's loyalty, innocense and unconditional love, and Russell's youthful joi de vivre, combine in a new subsitute for Ellie (almost like spiritual reincarnation), who was just as peppy and talkative, to ground Carl and prevent him from going off the rails.

It's not that Dug and Russel replaced Ellie. No one could ever do that. But they brought Ellie-esque comfort that Carl needed to become ok again.

Maybe the story is a kind of parable on the paradox of happiness? Let me explain.

Like pointed out in another message board, Charles Russel and Carl all three lack something and are obsessed trying to compensate for this privation. All of this is irrational and does not get to the root of the problem. Russel wants his last badge, trying to make his father love him, Charles wants his reputation back by capturing the bird, and Carl wants to get Ellie back by placing the house next to paradise falls. Because Russel is the youngest and the most flexible, he is the first who puts his obsession aside and stands up for Kevin. Of course Carl is so grumpy against him in the beginning because he does not want him to distract him from his last wish. He panders Russel for a while but is met with setback. Then he stubbornly chooses his house above Kevin, does not want to let go his admiration he once had for Muntz, and tries to move the increasingly heavy burden of his house.

But when he finally gets there, he begins to think about his stubbornness, realises how irrational he actually had been, and how even Ellie would not have wanted it. Then he decides to break with his past and the burden of his mourn by throwing out the furniture. Muntz does not make this realisation and does not break with his past, which drives him to lunacy. What he does not know is that the only way to catch the bird is that paradoxically, letting go of his obsession is the best way to obtain his objective, the way Russel did. What seemed impossible comes effortlessly, almost magically, when you would least expect it. I think this is the core message of the movie. This is not only true for Muntz: firstly Carl served as the father figure for Russel (and in fact Russel served as the child Carl never had, too) and secondly, Carl's house lands exactly where Ellie pictured it would on the moment he least expected it.

This is very similar to happiness, I think, which is something you will paradoxically be deprived of while you are desperately trying to obtain it, and comes when you least expect it.

"Paradise Falls" represents Eden (and how it fell)

The grape soda pin represents the 'club' that Carl and Ellie are in - the bond between them. And when Carl gives it to Russell at the end of the movie, it's now their bond.

The house was the most important symbol, representing Carl's connection with Ellie. It was where they first met, and where they spent their lives together. Then it sat stubbornly, refusing to budge, until it finally soared into the air, fulfilling Carl's promise to Ellie. And then at the end, Carl was able to leave it behind, getting on with his life without Ellie.