That was just utterly delightful.

The Tenth Doctor interacting with children in this way always takes me back to when I was a kid, and him trying to show them the joy of christmas without fully understanding what the kid wants is great.

And then the twist reveal that the child is dying, and wants to make it through the night, that this is all a dream for him. There's no logical explanation as to how this works, but the emotional weight carries it, and Ten going out of his way to make sure Christmas at the hospital is calm and working for him is just brilliant, the way it's written is nothing short of beautiful.