I recently ordered something that came in a big box. We kept the big box around for a few days and let the girls play with it. It was so funny to watch what they did with it.
One morning all three girls were entertained for a good while just hiding each other in there. They would tell me that I had a special gift, I would open the box and then they would scream and laugh. Variations included different combination of girls inside and the addition of blankets and pillows.
Andrew got to open a special gift when he came up for lunch that day.
All 3 were cozy inside.