In this movie they took them up in space. They're floating around and doing zero gravity stuff. Well, they had to do it all on wires. All the wires had to be painted black against this black background. If you didn't light it properly you could see the wires. Drove them crazy!
Also, if nothing else, writing this book has really changed the way I experience bookstores. I have a whole different appreciation for the amount of work packed into even the slimmest volume on the shelves.