Howard Attfield did film some scenes as Donna's father, Geoff Noble, but became too unwell to continue and died during filming. This episode was dedicated to him. Bernard Cribbins, who had starred in the previous episode Voyage of the Damned (2007), as a newspaper salesman named Wilfred Mott, was brought back to re-film Attfield's scenes, now establishing Wilfred as Donna's grandfather. The video release shows Attfield's scenes in a special feature.
Donna Noble was supposed to be a one-off character. Russell T. Davies was impressed with Catherine Tate's performance in The Runaway Bride (2006), that he decided to bring her back as a regular companion in Series 4. When they asked her to return, they didn't expect she would agree and had already written a different companion and chosen an actress to play her, only waiting on Tate's official denial to move forward.
Miss Foster was originally called Miss Rattigan. It was changed because Russell T. Davies felt that it better encapsulated her motherly role. The surname Rattigan would later be used in The Sontaran Stratagem (2008)/The Poison Sky (2008), the plot of which is referenced in this episode via the Atmos stickers in various car windows, most clearly the taxi that stops when the Adipose flood the street.
Just before the 28th minute of the episode, you can clearly hear the hitchhikers guide to the galaxy melody worked into the soundtrack.
Penny Carter was to be the name of the main companion of Series Four should Catherine Tate decide not to return as Donna Noble. The Penny Carter who appeared in Partners In Crime is altogether a different character that Russell T. Davies has devised.