Trivia: When Carl's house begins to lift and the little girl looks out her window, the Luxo ball from Pixar's other films is seen in her room.
Trivia: The Pizza Planet truck can be seen waiting at a stoplight when Carl's house first begins floating over the city.
Continuity mistake: When Mr Fredrickson opens the door there are 4 locks on the front door looking from the outside in. Next scene and consequent scenes there are only 3. (00:12:35)
Trivia: A scene in the airship of the dogs playing poker is a homage to the same named series of pictures painted by C.M. Coolidge. A further detail is that instead of having an ace up his sleeve, one of the dogs has the ace hidden in his collar.
Continuity mistake: When Russell is trying to mount the camping tend for the night, one of the stakes bounces on his face, giving him a bruise on the left eye, but in the next scene the bruise is gone.
Chosen answer: Carl and Ellie have two dramatically different personalities. Carl is more conservative, more reserved, a tender heart covered by a tough exterior which Ellie is able to break through, but which seems to recalcify after she dies. Ellie, on the other hand, is the sweet free spirit, rambunctious and adventurous. Throughout the film, each one conforms to the other until they ultimately blend into one beautiful unit. I think the makers of the film were trying to show that their respective personalities were a product of their upbringing, and reflected in the reactions of their families - hers larger, more fun, and more "hick" (we hear gunshots, for Pete's sake), and his more reserved, formal and patrician.
Michael Albert