I just ran across this idea at Smart Bottom Enterprises and it's SOOOOOO cute. I wish I had a little one around to make one for. But you wait, I'm going to keep this idea locked deep inside for 10 years down the road and my first grand baby is going to have one of these little doors.
Here is what it looks like on the wall with the door closed and the door open to expose the little bag to hold your little ones tooth.
Many people do Magic Leprechauns during March for St. Patrick Day visits, this would be the perfect addition for that as well. Be sure to check out the link above for the full set of instructions.