Abbate remembers, "Once we were given the green light to begin pre-production, Tim McCanlies and Brad started writing the script and working simultaneously with the story board artists. We began with just a treatment and Brad would bat ideas back and forth with the story board artists—it was an amazingly dynamic time, and it really allowed all of us to get into Brad’s head. We hammered away at it and by August, we had about 30 minutes of the film story boarded and we were given our green light to go into production."

The conscious decision had been made to create the majority of the main characters using the classic two-dimensional animation process. But even at the earliest stages of development, filmmakers were using technology to push the envelope of the classic animation process. Scenes begin to unfold during the story boarding phase as still pencil sketches; however, on "The Iron Giant," the artists enhanced the story reel (the filmed compilation of the pencil sketches) by adding camera moves and simple effects to the story board drawings, giving them the look of rough animation. Much of the mechanics and dynamics of the shots were worked out during this early stage.

From these early sketches, characters began to emerge.

Head of animation Tony Fucile was in charge of assembling the team of animators who created the characters and their world. He explains, "Once design begins on the characters and the look of each is approved, we wind up with something called model sheets, which function as blue prints for the character. Basically, character designs are taken and then rotated in space so animators can figure out how to draw them from all angles. We experiment with various emotions, facial expressions and body positions. This gives the animator more freedom, because he has studied what shapes are underneath the skull, how the ears are attached, that sort of thing."

The model sheets would prove even more valuable on this film, as Bird had chosen to give artists entire sequences (or chunks of the film), rather than assigning one head animator the responsibility for a particular character (as has become customary in recent films). Bird and Fucile worked side-by-side with the staff drawing the characters "on model," ensuring that the animators draw the characters in a homogenous style, downplaying their own differences in personal styles or ability.

"Everyone is trying, especially at the beginning, to figure out ‘how do I draw these characters?’ We have about 50 animators and 75 or so clean up artists [who literally ‘clean up’ the animator’s drawings], so we’ll have about 125 people working on the same character. We didn’t want Hogarth to suddenly turn into somebody else," comments Fucile.