The film centers on Carl Fredricksen (Asner), an elderly widower who travels to South America with youngster Russell (Nagai) in order to fulfill a promise that he made to his late wife Ellie.

It received acclaim for its screenplay, animation, characters, themes, narrative, emotional depth, humor, Asner's vocal performance, Giacchino's musical score, and its opening montage.

Ten-year-old Carl Fredricksen idolizes famed explorer Charles Muntz, who is discredited when a giant bird skeleton he brought back from Paradise Falls in South America is deemed a fake.

Russell, a young "Wilderness Explorer" scout attempting to earn his final merit badge for assisting the elderly, becomes an accidental stowaway.

Along the way, they encounter a giant, flightless bird whom Russell names Kevin (who they later realize is female) and Dug, a Golden Retriever whose collar has a device that translates his thoughts into human speech.

Other cast members include Mickie T. McGowan as police officer Edith, Danny Mann as construction worker Steve, Donald Fullilove (credited as "Don") and Jess Harnell as Shady Oaks nurses George and A.J., Josh Cooley as Muntz's dog Omega, and Docter himself, credited as camp master Strauch and uncredited as Kevin.

[29] The two men thought an old man was a good idea for a protagonist because they felt their experiences and the way they affect their view of the world was a rich source of humor.

After that they got the idea to use an old person, and found the contrast between the elderly grumpy man and the happy balloons in Docter's drawing appealing, inspiring them to work out his backstory.

The next concept introduced many of the elements that eventually made their way into the film, but had Carl and Russell landing the house on a Soviet-era spy airship camouflaged as a giant cloud rather than on a tepui.

Another idea Docter added, then removed, was magic fountain-of-youth eggs laid by the bird, in order to explain the age discrepancy between Muntz and Carl, but they decided this subplot was too distracting, and people would forgive the minor inconsistency.

[42] Knowledge of canine communication, body language and pack behaviors for the artists and animators to portray such thoughts came from consultant Dr. Ian Dunbar, veterinarian, dog behaviorist, and trainer.

[27] Docter encouraged Nagai to act physically as well as vocally when recording the role, lifting him upside down and tickling him for the scene where Russell encounters Kevin.

Docter wanted to push a stylized feel, particularly the way Carl's head is proportioned: he has a squarish appearance to symbolize his containment within his house, while Russell is rounded like a balloon.

[11] The challenge on Up was making these stylized characters feel natural,[17] although Docter remarked the effect came across better than animating the realistic humans from Toy Story, who suffered from the "uncanny valley".

What Pete Docter wanted most importantly out of the music was the emotion, so Giacchino wrote a character theme-based score that producer Jonas Rivera thought enhanced the story.

[68] It is the first score for a Pixar film to win the Oscar (Randy Newman also won for Monsters, Inc. and Toy Story 3, but in the category of Best Original Song).

[74] Despite Pixar's track record, Target Corporation and Walmart stocked few Up items, while its regular collaborator, Thinkway Toys, did not produce any merchandise, claiming the film's story was unusual and would be hard to promote.

[55] In Colombia, unexpected publicity for the film was generated due to the uncanny resemblance between Carl and Colombian ex-president Julio César Turbay Ayala.

The consensus reads; "An exciting, funny, and poignant adventure, Up offers an impeccably crafted story told with wit and arranged with depth, as well as yet another visual Pixar treat.

"[100] Although the San Francisco Chronicle noted that the film "contains many boring stretches of mindless freneticism and bland character interaction," it also declared that there are scenes in Up of "such beauty, economy and poetic wisdom that they belong in any anthology of great movie moments ... to watch Up with any attention is to be moved and astonished by the economy with which specific visuals are invested with emotion throughout [the film].

"[101] Variety enthused that "Up is an exceptionally refined picture; unlike so many animated films, it's not all about sensory bombardment and volume ... Unsurprisingly, no one puts a foot wrong here.

[104] Wall Street Journal editor Joe Morgenstern described Carl as gruff, comparing him to Buster Keaton, but adds that this begins to wear thin as the movie progresses.

[107] Entertainment Weekly editor Lisa Schwarzbaum described his appearance as a cross between Tracy and an eccentric out of a George Booth cartoon.

[109] He has also been compared to Walter Matthau, another inspiration for the character's design, by LA Weekly editor Scott Foundas, suggesting that actor Ed Asner was channeling him while performing the role of Carl.

In his book Disney, Pixar, and the Hidden Message of Children's Films, author M. Keith Booker described the love between Carl and Ellie as touching.

"[106] Chicago Tribune editor Michael Phillips praised the scene, describing it as an emotional and cinematic powerhouse, and that he also was nearly moved to tears.

However, Salon editor Stephanie Zacharek criticized the love between Carl and Ellie, describing their marriage as resembling a dental adhesive commercial more than a real relationship.

[156] The Redwood Creek Challenge Trail play area at Disney's California Adventure is themed after the Wilderness Explorers scouting organization from the film.

[157] In the episode "Loan-a Lisa" from the television series The Simpsons, the opening sequence of the film is parodied in a short of The Itchy & Scratchy Show titled "P.U.

[158] The fourth episode of the seventh season of the ABC fairytale drama Once Upon a Time, titled "Beauty" features a rendition of Up, with the characters of Rumplestiltskin and Belle taking the place of Carl and Ellie.