CGSociety has an excellent in-depth article where they talk to the the crew at Blue Sky Studios who worked on Horton Hears a Who! to find out what went into creating the unique look of the Who-world and its characters. The piece delves into the programming of the Seussian logic of exaggeration required to get the look of the book just right. Supervising animator Aaron J. Hartline’s knew this would be a big challenge because “everyone remembers Dr. Seuss from their childhood. It’s held so high, and you don’t want to ruin something that’s pretty sacred to a lot of people”.