D: How big is this world?
Me: Huge! Not as big as Saturn and the other big planets, though.
D: It’s bigger than Pluto though.
Me: Yes – because Pluto’s a dwarf planet isn’t it?
D: No! It’s just small. Mercury‘s like Earth, but all the people are really hot.
Me: Are they?
D: Yes, because it’s the closest to the sun. But it’s OK, it won’t melt, because it’s a METAL planet – it’s made from metal. But all the people on it are sad because they can’t have Christmas.
Me: Why is that?
D: Because all the snow would melt. So it snows, and straight away it melts. So they can’t have Christmas.