While the episode appears to follow immediately from the previous episode "School Reunion", Moffat says in the DVD audio commentary that when he wrote "The Girl in the Fireplace" he had not yet read the end of "School Reunion", hence the lack of Rose's continuing animosity shown towards Mickey after he joins the TARDIS crew. After reading the Doctor's mind, Reinette says "Doctor who?", a reference both to the series' title and to the long-running mystery about the Doctor's actual name. She also says that it is "more than just a secret", but does not elaborate further. Moffat said that he added the dialogue because he believes that because the Doctor does not tell even his closest companions his name, there must be a "dreadful secret" about it. Moffat also says that he did not include the word "Torchwood" (an "arc word" in the second series) in the script because Davies did not ask him to do so.