[2] While the core concept of the film was to have a house float into the sky with balloons, the filmmakers needed a rationale for why a character would do such a thing.
[3] Director Pete Docter always felt that an expository sequence to open the film was important because if the viewers do not love the characters, "then [they're] not along for the ride.
"[4] In an early draft of the Ellie–Carl meeting, Carl is trying to capture a bird with a trap and Ellie punches him in the face, yelling about animal rights.
This led into a montage sequence of a "lifelong sneak-attack punching game, lending the script some heart in a 'non-sappy' way", according to the Huffington Post.
[4] Co-director Bob Peterson said "we thought that was the funniest thing", noting that even when Carl visited Ellie's sickbed, she gives him a feeble slap.
[4] In one cutting room session, one part of the sequence in which Ellie is despondent having learned she is not able to have children, received many notes from members of the studio, believing the moment may have pushed things too far.
[9] In general definitions, the 'sequence' excludes the earlier parts of the film's prologue in which Carl watches a filmreel about Charles F Muntz and has a dialogue sequence with Ellie.
After fixing up the house where they met to match Ellie's childhood drawing, they spend their marriage doing three main activities: watching clouds, working at the zoo, and reading together.
As they fix up their house, where they will spend their retirement, Carl looks upon Ellie's art, representing her dream trip, and realizes he has yet to fulfill his promise, which almost stops the music entirely.
"[5] The musical themes established during this sequence play throughout the rest of the film, changing in timbre depending on the context, as an emotional anchor to the relationship of Ellie and Carl.
Roger Ebert praised the sequence in the film calling it "poetic and touching" and stating that it "deals with the life experience in a way that is almost never found in family animation".
[12][13] The Guardian described the sequence as "remarkable", "brilliant", and a "masterclass in narrative exposition" and thought the childlessness reveal would be emotionally affecting to the audience.