Here is a interview with Spike Jonzes on how the film came about:
How did the film come about?
I met Olympia in Paris through friends of mine. She was just starting to make the bags for her friends. She had a bunch of the scraps in her bag, all of the cut-out pieces of felt. I just loved it. I loved all the artwork she picked, the texture of it, the stitching of the felt. We joked about making a film and just went for it. It was this thing with no schedule, no pressure and no real reason to be—other than just that we thought it would be fun.
Did you write the story together?
Yeah we did. We would look at all the artwork over lunch whenever we would be in the same city, noting any ideas that would just make us smile. It was done like that, with no real plans.
What’s your creative process?
You just start with what the feeling is. For this one the feeling definitely started with the handmade aesthetic and charm of Olympia’s work. Instantly I had the idea of doing it in a bookstore after-hours, imagining the lights coming down and these guys off their books. Me and Olympia both wanted to make a love story, and it was fun to do it with these characters. It evolved naturally and it all just started with the feeling. From there you entertain yourself with ideas that excite you.
Do you go with your gut instinct?
If it cracks me up. We were talking about the skeleton coming off his book and the girl in the Dracula book waving at him. Olympia is someone who is just absurd, she’s used to just saying anything. She just started making the blowjob gesture as a joke to make us laugh but I was like, “We’ve got to do that.” It’s about taking things that could just be a joke while brainstorming and actually going for it and using it.
What inspires you?
People inspire me. Humberto Leon and Carol Lim [from Opening Ceremony] and the confidence and creativity in how they run their business. Pixar’s really inspiring, they make films in the best possible way. They’re always focused on story. I could list a million people that inspire me all the time. David Bowie’s music, Charlie Kauffman, David Russell. A lot of people that I work with too, just conversations I have with them about what we want to do.