"I promise to capture the beast, alive !"

"I'm taking him back with me, alive, or dead !!!"
Shows how far gone he is.

My problem with a lot of stories with the message "just let go of the past" is the past will haunt you in more ways than mental. If Charles Muntz tried to make some other scientific discovery to regain his image no one would trust him, they'd just bring up the fabricated bird controversy and discredit him.

To think Charles Muntz is both: "Never meet your heroes" and "you either die a hero or live long enough to become the villain"

Yeah, I really admire how well written Muntz is as he's supposedly an idol of the protagonist and wants to be like him. And as the story progresses, Carl finds that his childhood hero isn't that what he was back then. Because Muntz had basically cut himself off from the world and has only focused on one thing in life. To regain his reputation.

The worst part of Muntz offing the other explorers is... they probably weren't after the bird at all.
He names their "excuses" - drawing maps, catalouging plants - and they are perfectly logical reasons for them to be there. His discovery was called a fraud, nobody was coming for a bird that wasn't supposed to exist. It's a jungle. It is full of fantastic scientific discoveries. And yet, Charles is so obsessed with capturing the bird and proving everybody wrong he just doesn't acknowledge this possibility. He sees other people near his hideout and flips the heII out. His stubborn paranoia urged him to turn on people who were never enemies to begin with.

It's not just that he made dogs talk. He was using an instantanious universal translator, in the 70's! wicht means he probably made it in the 50's or ever earlier. That shit would have chanched the world in ways I cant even imagine.

This is why people say, "Never meet your heroes."

I'll admit It took me some years to realize it, but i find brilliant and a little sad how Muntz was destined to never catch Kevin, not because the bird didn't want to be near him, but because he never carried chocolate with him due to the risk of one or more dogs eating it and dying of poisoning, i would even bet he probably forgot chocolate existed after decades of cutting off communication with the world.

Fun fact: there was actually a plan to redeem Muntz that was storyboarded, and voice acted.

An extra brilliance as to why Muntz didn't have chocolate to use to attract Kevin is because he has a boatload of dogs, WHICH CANNOT EAT CHOCOLATE WITHOUT BECOMING DEATHLY ILL.

Love how you brought up Muntz's inventions. What interesting about this film is that no one ever explicitly states in the story that Muntz could've created a whole new life for himself with all the dog inventions he made. It's only implied for the audience to pick up on, and yes, it makes him that much more tragic when you see how his inventions could've revolutionized the world.
I also like how Disney's come full circle and recently reacquired the rights to Oswald the Lucky Rabbit! :)

Charles Muntz must've been a breeder if he was able to live with that many dogs.

Btw, it's a shame they went with the weakest ending for Muntz for the final cut of the movie, there were 2 alternate ending, both a lot stronger.
1) He chases the bird into the labyrith, which WAS SET UP EARLIER IN THE MOVIE to be inescapable - something which in the final cut is pointless - and remains trapped in there, never to come out again, chasing his goal for the rest of his life.
2) He and Carl had a heart to heart about the nature of loss, with Muntz accusing "you dont know what its like to lose everything" and Carl responding that he DOES know what its like to lose everything, and that he lost his wife. Leading into the two characters actually reconciling and Muntz realising that his pain, is not unique.

So he was kicked off his property for defending it from someone who was destroying it? New York, definitely New York.

Even if he comes back with his “discovery” he’d go back to a world that has changed and I don’t think there’ll be anyone at that time would be left for him.

This is why I always tell people that no matter how tragic or messed thier past might have been, you eventually have to learn to let it go and move on no matter how sad or horrible. Yes, you don't have to forget the past, but don't let it control and consume you  in the present. It may be tough, but it just isn't worth letting your future getting ruined from it

The original ending would have actually have Carl talk down Muntz as they both accept their grief and moved on. Even though I love Up as is, I kind of wish they stuck with that ending since it could arguablely be more powerful for Muntz to finally let go of the past or even break down realizing how much of his life was wasted for a meaningless mission.

I think the key to Carl being able to go and Muntz's inability to was the fact that Carl was loved while Muntz was alone and forgotten (besides the dogs, who he treated as servants anyway). Carl's ability to let go of his grief was when he finally turned what he'd thought was the last page of Ellie's adventure book and saw that she'd added things--things showing that her true adventure was her marriage to and life with Carl, not the dream of going to Paradise Falls. Muntz didn't have anyone to show him how amazing he was even without Kevin's species.

I like how “Up” is ironic as it is the single word that describes the theme of to be in the present, you need to not carry any weight; lift yourself ‘up’.

Charles Muntz also serves as a great reminder, that a man can go crazy if his reputation gets destroyed.