Continuity mistake: In the scene when Donna asks the woman if she could borrow £10 because it's Christmas, you can see that Donna is wearing sports shoes instead of her usual white wedding shoes.
Continuity mistake: When the Doctor picks up a mug and a pencil to use as props to explain to Donna how she was pulled into the TARDIS, he is initially holding the pencil by the blunt end. The scene cuts to a shot of his face, and suddenly he's holding it by the sharpened end.
Continuity mistake: The episode repeats the closing scene of "Doomsday", when Donna unexpectedly appears in the TARDIS. However, several details are different. One, the console room is more brightly lit than in the previous episode. Two, the shirt belonging to Rose that Donna finds draped over a railing was not present. Three, the Doctor's coat (draped over a ceiling support) has shifted in place, despite not being touched.