He is an explorer, obsessed with finding the beast of Paradise Falls ever since he was accused of fabricating its skeleton by the National Explorer's Society and stripped of his membership. He then vows to find the bird and catch it to prove it is real. He travels in a dirigible called the Spirit of Adventure, and has many canine minions who wear collars that allow them to speak.
When the heroes of the story Carl and Russell meet him years after he departed to capture the beast of Paradise Falls, they find he has gone insane and is now quite paranoid, killing innocent people he thought were going to steal the bird. Soon, with Kevin, a light appears and Muntz tells his dogs to get him and Kevin got captured by him. Since, in the final battle, Carl was fighting him with his cane and Muntz uses a sword, nearly killing Carl.
Eventually the blimp is turned sideways, saving Carl. Carl and Russell trick Muntz into following them into the house floating next to the blimp. Before Carl and Russell can escape in the house with the bird, Muntz retrieves a lever-action rifle and begins firing at the two. Muntz gets the upper hand until Carl tricks him into going into the house, which Carl promptly sends floating away after having Russell and Kevin escape back onto the Spirit of Adventure. When Muntz realizes that he has been duped, he leaps out of the window in an attempt to get back to his airship, but his foot gets tangled up in some balloon strings and they snap and he falls thousands of feet below to his death.
Muntz is best described as determined, paranoid, insane, selfish, greedy, violent, bitter, charismatic, decieving, angry, ruthless, intelligent and dangerous.
Muntz is a brave and charismatic explorer with a genuine passion for discovering new things. When Carl Fredricksen and Russell meet him for the first time, he seems like a benign, charming gentleman. However they soon discover that his obsession with capturing the bird of Paradise Falls has unhinged his mind and driven him insane. An extremely proud man, Muntz is consumed with bitterness and rage over being expelled from the National Explorer's Society and will stop at nothing to restore his reputation, even if it means murder. Nevertheless, he is polite and affable as long as people do not interfere with his plans. Muntz's pride and obsession give him a striking similarity to Captain Ahab from Moby Dick. He also evidences a genius level of intellect, able to programme dogs to talk and building his own airship.
However, others have seen a more rational side to the character. Spike.com ranks him 4th in their list "The Top 10 Hollywood "Villains Who Got Totally Screwed". Under the section titled "What People Forget", it says "He never actually did anything altogether evil until the main characters boarded his zeppelin by force and attempted to steal his bird, at which point he tried to throw them overboard. What one has to understand is that he spent over 50 years trying to catch that bird. 50 years in the jungle trying to catch the damn thing and now that he has, some kid and an old guy that smells like prunes are trying to steal it back from him? He’s completely within his rights to have that bird on his ship! It was a legitimate capture in the name of science, and they’re trying to stop him because they think that’s mean? He didn’t even plan on killing the thing. He just wanted to get back his respect from the scientific community. Sure it’s implied that he attacked the other people who he thought were trying to take his discovery from him, but we aren’t given any details, so for all we know he just chased them off with his cane."
If Carl is 78 by the time of him meeting him, and Muntz was at least 20 when Carl was 8. It's possible that Muntz could be over ninety years old.
When talking to Carl, Muntz talks about being on Safari with Roosevelt. It is hard to tell if he means Theodore Roosevelt or one of Roosevelt's sons or his nephew, Franklin Delano Roosevelt, as Theodore Roosevelt passed away in 1919, when Charles was only 3 years old.
An explanation for Muntz's advanced age is in a deleted subplot from Up. Turns out that Kevin's eggs act like a sort of fountain of youth that prevent Muntz from aging.
- Charles F. Muntz is currently the first and so far the only Pixar antagonist to use a fire weapon (a sniper rifle). It is an 1874 Sharps chambered for .45-70.
- The sword Muntz uses is a medieval Claymore.
- The ultimate fate of Muntz was a work in progress for Pixar as they tried several versions to get him out of the way so the film could get back to Carl and his connection to Ellie. First they tried giving Muntz a chance to redeem himself to the point where it resorted to just him talking with Carl. Then they tried an ending that was reminiscent of Stanley Kubrick's version of The Shining where Muntz goes after Kevin in the labyrinth, where he's left to wander forever, but it felt more like Muntz's ending than Carl's ending. At that point, Pixar decided to place the climax on the Spirit of Adventure and one version had Muntz trapped in the house as it floats away, but it felt wrong due to the house being seen as Ellie. Another version had Muntz caught in a bunch a balloons and floating upwards, but it left an uncertainty as to whether he was dead. It was at this point that Pixar decided the best comeuppance for Muntz was for him to get caught in the balloons and fall with them. This is discussed on the DVD extra "The Many Endings of Muntz".
- The name "Charles Muntz" is based on "Charles Mintz" whom Walt Disney worked for while making the Oswald the Lucky Rabbit cartoons, and who took the cartoon from Walt Disney since Universal Studios owned the copyrights.
- Muntz is based on aviator Howard Hughes who was known for his intelligence, eccentricity, ego and obsessiveness. He also has traits of real life adventurers, Charles Lindbergh and Percy Fawcett.
- He is the first Pixar villain to fall to his death, the third Pixar villain to die, and the sixth Pixar character to die.
- Charles Muntz is similar to Syndrome from the Incredibles in several aspects.
- Both were given a sympathetic backstory (Muntz being labeled as a fraud while Syndrome being cruelly rejected by his number one fan).
- Both are serial killers.
- Both are willing to kill children (Russell in the case of Charles Muntz and Dash and Violet in the case of Syndrome).
- Syndrome was Mr. Incredible's number one fan, while Carl was Charles Muntz' number one fan.
- Both own a flying vehicle (in Charles Muntz's case, the Spirit Of Adventure).
- Both have a large amount of evil minions to do their bidding.
- Syndrome died when his cape snagged on a jet turbine, while Charles Muntz died when he got snagged on balloons.
- Both have had one of their minions betray them (Dug in his case and Mirage in Syndrome's case).
- He is one of if not the darkest Pixar villain
- Charles Muntz become Thomas and Twilight Sparkle's enemy in Thomas and Twilight Sparkle go Up.