Their "elves on the shelf" are named Billy and Wayne. (Their maternal grandfather's first and middle names.)
The girls asked their parents: "Do you have elves?"
The answer is: "Yes, we do."
The next question: "What are their names?"
The answers are: "Harry and Jewel." (Paternal great-grandfather's name and maternal Grandmother's name.)
The nieces ask: "Why have we never seen them?"
The answer is: "Because we are grown up."
The girls ask: "Even if you are grown up, can they come see you?"
The answer is: "Yes, they can."
And we know this to be true, because Harry and Jewel appeared with Billy and Wayne this week. OMG!
The next question from the nieces: "Do Uncle Steve and Aunt Cindy have elves?"