The film was originally done in pencil test, without color. Many of the original drawings were lost in transit when Pete Docter mailed them to Canada after Mike and Spike offered to color it to include it in their animation festival. With the blessing of Pixar, for whom Docter was already working at the time, and after some convincing from his mother, the missing drawings were recreated and the color version completed.
Made by Pete Docter while he was in CalArts.