The idea

When I was done with the drawings for my picture book Amandina, my wonderful editor Neal Porter was wondering (being wonderful) if I had any idea for the next story. I did have a few, but at a very rough stage.
In Amandina, Neal especially liked this drawing:

So he told me: why don't you think of a story about a magical suitcase? I thought about it for a couple of weeks and then I went back to him with a manuscript and some quick sketches.

Neal liked what he saw and helped me shape it (here's one of his sophisticated visual suggestions).

After everything was set, I began working on the final drawings.