
SHE'S HIS FUCKING WIFE!!
She's not Rose, she's not Jenny, she's not the Rani, she's not Romana. River Song is the Doctor's wife from the future. She's going to die in the next episode. He will spend all that time with her, doing all that funstuff in her diary, knowing precisely how and when she will inevitably die.
Paradoxes, inevitability, fate, curse of a Time Lord... Jesus Christ to hear fandom talking you'd think they'd never seen a Moffat episode before.
EDITED TO ADD SOMETHING I POSTED IN THE COMMENTS: I don't understand what everyone's so worked up about, she's not the next companion, she's his lover/wife from some point in the future. We'll more than likely never see her again. It's about time travel and the weirdness involved. It's about the Doctor losing the woman he loves, BEFORE HE LOVES HER. It's about her dying in the arms of a man WHO DOESN'T LOVE HER YET. It's a timey-wimey Moffat story, nothing more.
Moffat's apparent fascination with the mechanics of time travel make me tremendously excited about his tenure as boss. I think if Moffat does go for any sort of overriding story arc, it will be far more clever than Rusty's namechecking "Torchwood" every bloody episode, and will probably deal with the same themes he seems so fond of, fixed history, inevitability of events, consequences of past and future actions. I'm excited about Moffat, really I am.