Elf on a Shelf

We started elf on a shelf with the girls this year.
It's pretty nice, the girls get excited find their elf Krystal.
The story goes the elf comes to life once he or she is named. ( you have to register them with the North Pole)
At night while the kids are sleeping the elf goes to the North Pole to report back to Santa on the behavior of the kids.
When the elf returns home the elf gets bored and into things. But freezes when the kids start to get up..
Here are something's Krystal has done..