Oh, boy, do kids get clever as they get older. They start paying attention to the details.
We have gas logs instead of a traditional fireplace. And our gas logs are not open like a traditional fireplace, there's a glass panel in front. And Mister J is concerned that Santa will not be able to deliver gifts because the glass will keep him from getting into our house.
Rest assured, I have explained to the children (Miss M, upon hearing Mister J's concerns, also became quite worried) that Santa is magical, and will indeed be able to deliver gifts for Christmas morning.
One of the best gifts I'll get - seeing their minds at work. It might make my job a bit harder (they ask lots of questions), but I sure am proud of them!