The barn/animal shelter part of the set has a little hole in the back where a light can be put in and shine through the star-shaped opening in front, for the better guidance of a trio of either monarchs or Zoroastrians.
In past generations, they'd used a cord with a single Christmas tree light to light it up, but in the 21st century, I figured it was time for something better. By which I mean, of course, time to throw vastly too much technology at the problem.
We had some battery powered tea lights kicking around, which seemed about right, but how to get one to shine through the hole? My first thought was to make a tall stand for the light with the 3d printer. However, that turned out to be just slightly bigger than the largest dimension my printer could handle, so I had to rethink the design. What I settled on was a holder for the tea light with a little clip on the front so that it could hang on the edge of the hole. It's ultimately a better design, since it uses far less material than the freestanding approach would have.
Turn it on, and you get the warm flickering glow of a far-off nova shining on a bunch of plaster figures.
So merry cookie season, everyone!