These paper dolls are from a book by M. A. Glen that's available on several public domain book sites (the copyright date is 1907), but they weren't exactly print-optimized. I've removed the old-book yellowed background and done a couple of other minor enhancements for the sake of print quality, and I'm putting them up here to share! Sorry for the quality of the example photo above; my camera is broken and the tablet isn't the best for taking pictures. Anyway, the original instructions use Mary and the lamb as an example and say the following:
Cut out the two double figures. Fold on the dotted lines marked A A A A so that the upper part of each of the four figures projects forward as shown in the small picture X. Fold on the lines marked B B where the figures join each other so that the colored surfaces face outward, and then, beginning at the feet, paste the front view of Mary to the back view of the lamb as far as the dotted lines A A. In the same way paste the front view of the lamb to the back view of Mary—as far up as the lines A A. Now paste together the front and back of the upper part of Mary. Then paste together the front and back of the upper part of the lamb. Cut off the letters A A A A B B.
Now if the lamb is held by the feet and turned inside out, Mary will appear, and vice versa. MAKE ALL THE OTHER CHANGELINGS IN PRECISELY THE SAME WAY.
The Changelings will stand alone. If they do not stand firmly after you have turned them, pinch them slightly along the dotted lines that were marked A A A A.
Look carefully at the finished Changeling in the front of the book. It will help you to make all the Magic Changelings.
I didn't see any finished doll at the front of the book, but I've shown a picture of my first attempt at Mary and her lamb, spread out in such a way that you should be able to see what it's talking about. Essentially, you need to glue the parts that are already attached at the feet back to back as far as the line, then glue the back of each head to its matching front. If you've done it correctly, the whole doll will be shaped like an X and can then be flipped to show either of the two characters. Here are the first three; I thought that all twelve of them would make too long of a blog post, but the others will follow soon. I've reordered the ones after Mary and her lamb, but the other two I'm posting now are Tom the piper's son with the stolen pig and Goldilocks (or Silverhair) with the baby bear. Print them out and enjoy!