This morning, when I woke Kylie, our nine year old daughter, she hit me with some Tooth Fairy questions: "Do you believe in the Tooth Fairy?" "How can she be real, she'd be busy all the time with millions of kids losing their teeth every day!" "If she's real, she'd never forget a kid, right?"
Odd, but with Kylie, you're never sure what you'll get in the morning. So we went through the morning's tasks, getting ready for school, and then she hits me with: "Dad, there's no way the Tooth Fairy is real, and I've got proof…right here!" And she pulls out her Tooth Fairy pillow, where you place teeth for the Tooth Fairy to collect and replace with coins.
She then pulls a tooth out of the pocket of the pillow, and says "This is my tooth; it fell out yesterday, and I didn't tell you or Mom. Then I put it under my pillow last night, and the Tooth Fairy didn't take it!"
At that point, I took her into the other room, so our younger daughter wouldn't hear, and explained that yes, the Tooth Fairy was really Mom and Dad, and we did it to help our kids through what can sometimes be a bit of a traumatic experience. I asked her to keep this secret from her sister, and she merrily agreed.
This one's got a future in science, I think! (I also realized that had I noticed the missing tooth, and managed not to say anything to her, she would've woken up today absolutely convinced that the Tooth Fairy really exists!)