Billie Piper admitted that she had forgotten how to play Rose, and needed to watch past episodes to remind herself. She noticeably lost her accent and speaks with a lisp, which she claims was because it was cold as they were shooting in winter, and she was wearing a "tiny jacket".
Russell T. Davies considered exploring how stories set in the past or on other planets would be affected - such as having UNIT send "time commandos" to the year 1599 to foil the plot of the Carrionites, in The Shakespeare Code (2007). Ultimately, however, he decided that this would cause an already very self-referential episode to become unnecessarily obsessed with minutiae, and Davies was very concerned about the ability of casual viewers to immerse themselves in the storyline.
Donna's conversation with Rose on the bench was supposed to be performed at Thompson Park. However, Catherine Tate had come down with influenza, and so it was decided that she would be more comfortable if recording instead proceeded at Sophia Gardens, which was being used as the production unit base.