Fridge riddle

I was sitting at my makeshift breakfast bar this morning, sipping coffee and contemplating floor tiles and radiant heat, when I glanced at the refrigerator (the only remaining appliance in the room) and noticed something odd that appeared overnight.

   "Honey?" I called to my spouse. "When did we get grandchildren?"
   "We didn't," he replied. "Not that I can recall, anyway."
    Hmm. I'm going to need another cup of coffee to figure this one out.