"The magician in this house...

has gone off for a nap. He has been working hard changing these frogs into chocolate. Please help yourselves - one for each paw!" 
I made the notice up and stuck it to the front door. I put a bowl of chocolate frogs on the mat. I prowled off to catch up on some late e-mail. The Senior Cat read and snoozed.
I heard footsteps and giggles and then silence and then more giggles. Some time later it was repeated and then again. 
I went off to bed to read for a bit but I left the light over the front door on for a while. Parents had warned me "it could be as late as ten" and I knew it might be even later. 
I fell asleep and woke again just after midnight. I crawled out of bed and prowled out to turn the light off. I didn't bother to look until this morning. 
The frogs had gone. The notice had gone too. Stuck on the door there was a note reading,
"The magic stops working at midnight!"
And, in much smaller print, "Frogs have all been adopted equally".
I had added up all the children in the street and the next street. I had multiplied by two and added a few extra. It seems the magic worked about right.