A couple of years ago, I made a small Tooth Fairy Monster tote for my granddaughter.
Since she likes to journal, I placed a small notebook and pen for her to write about each time she lost a tooth.The Monster mouth was made into a pocket to hold the tooth.

Well, it is Tooth Fairy Monster time again, but this time, for my grandson. Yesterday, he proudly showed me that he is ready to lose a tooth. I offered to make him a pillow, and he readily accepted. He did suggest that a zipper pocket would ensure that the tooth did not fall out of the pocket and get lost.
So, when I returned home, I researched different styles of tooth pillows online. Then, I studied tutorials on how to make zippered pockets. After a fun evening of planning, I drew up a pattern and prepared to start on the pillow today. I was a bit hesitant when it came to making the zippered pocket. But it was easier than I thought.
  
Tooth Fairy Monster Pillow