Here I am trying to be good and not post all of mine at once. That was the next one I was going to drop in here. Aw who cares... it's brilliant stuff!!!
Heh, when Davros asked the Doctor if he had any Pop Tarts, I thought he was going to amke a reference to Rose ("Nah, no Pop Tarts, she let a couple seasons ago")
The doctor's there because he just had an adventure with Kate. Her DNA was going to be overwritten by her ring which was previously worn by Diana.