The oversized hardcover version of The Promise offers up plenty of details on art design. It also includes a all three volumes of the graphic novel, completely annotated by author Gene Luen Yang and artist Gurihiru.
On finding the right art style:
Because of other projects we had been working on at the time, we drew everyone's heads too big at first, especially Aang's. The characters ended up looking too childish, so we went back and fixed this. We worked especially hard on Aang, since it was so important that we get him right.
On drawing Sokka:
We really enjoyed drawing Sokka. We based his costume on the design of his father's costume, so that you could feel the bond between them.
On keeping the action flowing:
We always think about how to draw the residers' eyes along the page when we do the Layouts.
On juggling such a large cast:
We sent several cover ideas for each part of The Promise. It was very challenging to fit all five characters on each cover.
On using historical watersheds as inspiration:
The Harmony Restoration Movement was inspired by various movements that China went through in the 1800s and the early 1900s. After suffering humiliating military losses at the hands of foreign powers, the Chinese tried to get their country back on track with different programs. The Self-Strengthening Movement is one example; the May Fourth Movement is another. At the beginning of The Promise, the Earth Kingdom is in a position similar to that of late 1800s China.
On growing up:
I loved how the original show referenced American coming-of-age milestones. "The Beach" features a high-school house party. In "Nightmares and Daydreams," Aang suffers that familiar nightmare of being pantsless at your final exam. Aang's final confrontation with Ozai is his final exam, and Zuko's coronation is their graduation ceremony. So what happens on this page? Partying on grad night!