The Doctor's asking Gwen if she's from an old Cardiff family is a reference back to The Unquiet Dead (2005), in which Eve Myles played the clairvoyant Gwyneth.
The full dialogue for the German Daleks is as follows: "Exterminieren! Exterminieren! Halt! Sonst werden wir Sie exterminieren! Sie sind jetzt ein Gefangener der Daleks! Exterminieren! Exterminieren!" This translates as: "Exterminate! Exterminate! Stop! Or you will be exterminated. You are a prisoner of the Daleks. Exterminate! Exterminate!".
The original script contained the following dialogue for the scene in The Crucible.
Rose: "So how was that sentence going to end?"
The Doctor: "Which one?"
Rose: The one that started with 'Rose Tyler'?"
The Doctor: "'...it's cold out.'"
Rose: "Seriously!"
The Doctor: "Does it really need saying?"
Rose: "Yes."
Davros: "Such intimacy with your companions, Doctor. So different from the man I once knew."
The original ending featured the Doctor in the TARDIS, when a scanner begins receiving a strange signal, prompting the Doctor to launch into his traditional "What? What? What?" response, after which two Cybermen suddenly rise up behind him - a cliffhanger. Russell T. Davies explained that the cliffhanger ending was dropped in response to comments by Ben Cook, a writer with Doctor Who Magazine, who stated a cliffhanger was inappropriate after such a sad series of scenes. Had the Cybermen scene been kept, this would have marked the first time since Doomsday (2006) that both Daleks and Cybermen had appeared in the same episode, and the first time Cybermen would have appeared in the same episode with Davros.
The musical score that is being played when the TARDIS tows the earth home is the same musical arrangement for the "Song" that the Ood sing after the circle has been broken (Planet of the Ood (2008)), only with different percussion.