Continuity mistake: When Donna is sneaking around the Sontaran ship, she's carrying Martha's old phone, which she's using to stay in touch with the Doctor, and the rubber mallet from the TARDIS. There are times when one of the two objects, the phone more often, is missing from her hands with no explanation.
Continuity mistake: When Private Harris orders the two hypnotized workers in the basement of the ATMOS factory to let him through the door they're guarding, he's holding a torch in his left hand, and when shown from behind has that hand down by his side. In the Sontarans' video feed, which also shows him from behind, his left hand is on his assault rifle.
Continuity mistake: When the Doctor gets embarrassed as Donna lightly mocks him for not realizing that when she said she wanted to go home, she only meant for a brief visit, he rubs his chin with his left hand. When Ross Jenkins interrupts by saying, "Ready when you are, sir," the Doctor is now rubbing his chin with his right hand. In the shot after that, it's back to his left hand.
Continuity mistake: When the Doctor opens a shipping container full of Ood and he and Donna stand in the entryway, he only opens the right-hand door, leaving the other one shut. In a shot from behind the two of them, facing into the crate, the left-hand door is now wide open.
Continuity mistake: When Ood Sigma steps in front of Mr. Halpen while he's holding the Doctor and Donna at gunpoint and suggests he have a drink, the glass Sigma holds up is empty, despite the fact that he was heard pouring Halpen's tonic into it just moments before. In a shot later in the scene, the glass is shown full.
Continuity mistake: When the Sybilline priestesses kneel after the High Priestess speaks, in a shot from the front, Donna, sitting on the altar, has her hands in front of her - she's using her left hand to take the rope off her right wrist. In the next shot, from behind, her hands are at her sides. In addition, the rope still on her right wrist disappears.
Revealing mistake: When the Doctor and Donna are walking through the underground tunnels towards Mount Vesuvius, tunnels that can be presumed to be fairly warm due to their connections to volcanic activity, their breath is visible - something that only happens in cold temperatures.
Continuity mistake: When the Doctor and Donna leave as Caecilius, Metella, Evelina and Quintus stand and watch the destruction of Pompeii, the TARDIS changes orientation between shots - in both of them, one from in front of the family and one from behind, the TARDIS' door, with the sign, is visible.
Continuity mistake: When the Doctor and Donna are talking to Caecilius, when they introduce themselves as "Spartacus" and Caecilius makes several guesses as to their relationship, wondering if they're married or siblings, in shots facing them, the Doctor and Donna are standing fairly close together. In shots facing Caecilius, however, the Doctor and Donna are standing much further apart.
Continuity mistake: After Lucius' arrival, when the Doctor escorts Donna towards the TARDIS, telling her they have to go, which she doesn't agree with, between shots his hands change position between having his right hand on her back, or having both his hands on her shoulders.