You Are Not Alone
The Companion for this story, played by the wonderful Catherine Tate, starts us off, walking down the aisle, neon family either side. She's always been stable, always kept her valence shell full, non-reactive; until she met Lance, until she met our Doctor, she was odorless, colorless, monatomic -- but that's not why her name is Donna Noble. In every chapter of this story, you'll find a hymn: sometimes they're more hidden than others. Sometimes they're profane. But this is the Christmas Special, and so this is Donna Noble: give us peace. The first thing she does is open the doors of the TARDIS wide, and let some air in.
After Donna's been kidnapped by the pilot fish Santabots, there's an excellent scene in which the TARDIS physically comes bouncing down the highway, careening after her. They showed this at Children In Need; I watched it on the web, and it was amazing: the TARDIS comes careening down the motorway, music so crazy you couldn't really hear what was going on, on the screen. But in the crowd: everybody in the whole concert hall, gasping at once, breathing with a single breath. It was huge. The moment made me understand Doctor Who fandom a whole lot more. Think about the power of that moment: when the TARDIS comes into the shot, and the whole world starts cheering, all of them in love with exactly the same thing, at exactly the same time. And from one kidnapper to another, the Doctor asks Donna to jump. She asks if his "friend," whose name he hasn't yet said, trusted him too. Did she jump? Did she ever.
Being a normal person -- a person who didn't notice the Santa Fish or the Slitheen or any of that shit -- doesn't make you less. It makes you Donna, which you already were. "The Oncoming Storm" isn't bullshit mythology, it's the way of things. But just like the Time War, which hurt everybody but the normal people, the Doctor comes in waves. There's a trees/forest analogy running through the season, and Donna starts it here. The trees are made of forest, and the forest is made of trees. No trees, no forest: but without a forest, the wind can take you down, one by one.