A few observations on Up:

• Maybe unusual for a road movie, most of the action occurs in the first and last mile (mostly last) of the journey, and we know absolutely nothing of what happens during the roughly 3500 miles in the middle.
• As Eiko pointed out, neither Carl nor Russell eat anything during the presumably multi-day journey, even though Russell is feeding chocolate to Kevin through much of the second half. They only even show signs of hunger when offered a meal by Charles Muntz, which for various reasons they’re unable to eat.
• In a movie in which humans, dogs and houses can fly, a movie entirely consumed with the sky, the only consequential bird is flightless.