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. (00:11:05)
Continuity mistake: When the Doctor interrupts Mr. Copper's incredibly inaccurate description of Earth society to ask him where he got his information from, in a shot facing Mr. Copper, the Doctor's raised hand has only one finger extended. In the next shot, facing the Doctor, he has two fingers extended, with the other two only loosely curled. Shortly after this, the Doctor scratches his temple with that same hand, only for it to be absent in the next shot facing Mr. Copper. (00:11:40)
Continuity mistake: After Milo and Cheen abduct Martha, they put a sleep patch on her before entering their car. In the close-up where Cheen applies the patch, it's stuck on securely and neatly, with the top and bottom of the square pointing directly at Martha's head and chest respectively. In a wide shot immediately afterwards, the patch is stuck on quite loosely and has gone askew. (00:06:35)
Continuity mistake: When the Doctor and Martha open the doors to the balcony, in a shot facing them, Martha lets go of the handle of her door and it swings completely open. In the next shot, from behind, Martha is still holding the doorknob. (00:10:35)
Continuity mistake: When the Doctor is looking out the window while asking Martha if there's a balcony on the floor of the hospital they're on, in close-ups of him only his right hand is visible, resting on the sill between two windowpanes, and his left arm is by his side. In a wide shot from outside looking in, his left arm is stretched out with his left hand gripping the divider between two windowpanes, in a spot where it should have been visible in the preceding shot. (00:10:05)
Continuity mistake: When the Doctor takes a swipe out of a jar of jam in Trish's kitchen and sticks his finger in his mouth, he only has his index finger in his mouth. The scene cuts to Rose giving him a "WTF" look, and when it cuts back to the Doctor he suddenly has two fingers in his mouth. (00:21:15)
Continuity mistake: When Jake turns on the light in the cabinet with the Cyberman on the zeppelin's bridge, he's holding his handgun in his left hand. The scene cuts away to Mickey briefly, and when it cuts back to Jake his gun has jumped to his right hand. (00:24:30)
The Girl in the Fireplace - S2-E7
Continuity mistake: For most of the scene where he's probing Reinette's mind to find out what the clockwork droids want with her, placing his hands on her temples, the Doctor's left hand is positioned with two fingers on either side of her ear. When he realises that she's seeing some of his memories, his ring finger has jumped to being in front of her ear, without him taking his hands from her head. (00:20:50)
Continuity mistake: When the Doctor is restrained by two of the Editor's corpse minions, and the Editor demands to know who he is, the hand of the one holding the Doctor's right arm moves between his chest and shoulder several times. (00:30:50)
Continuity mistake: When the Doctor is leaving Roger's house, a gadget in his pocket starts beeping. He pulls the device out with his left hand, but in a close-up of it immediately afterwards, it's in his right hand. (00:07:35)
The Family of Blood (2) - S3-E9
Continuity mistake: When Martha finishes listing off the bones of the hand to Joan, in order to prove that she's a medical student from the future, in a shot facing Joan, Martha's thumb is extended. In the next shot, facing Martha, her thumb is suddenly folded back, as if she was using her hand to display the number 4. (00:12:15)
Revealing mistake: When the Gamestation's transmissions are cut off by solar flares, there is a close-up of a screen going over to static. In the upper right corner, a box with "Play" written in it is visible, revealing the image on the screen as a video. (00:34:50)
Continuity mistake: When the Doctor sonics the payphone so Donna can call her mother, he's doing it with his right arm, then it cuts to close-up and he's using his left arm. (00:09:00)
The Impossible Planet (1) - S2-E11
Continuity mistake: In shots of the base's Ood habitation area from above, the Ood are shown in four rows from left to right, with the Ood in the third row standing with their backs against the room's middle partition and the other rows sitting on benches. However, in a shot from inside the lower area when the Doctor and Rose first go to Ood habitation, the third row is shown sitting as well. Not until later in the episode, when Danny is ordering the Ood to remain in the room, is the third row shown standing again. (00:25:15)
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. (00:01:15)
Visible crew/equipment: When Rose and the Doctor are riding after landing, you see the camera, crew and lighting equipment reflected in their glasses. (00:04:00)
The Christmas Invasion - S2-E2
Revealing mistake: When Daniel Llewellyn is looking up U.N.I.T. staff records on the computer, at one point a control panel for a DVD playing program is visible onscreen, showing that the special U.N.I.T. user interface is a video. (00:26:25)
Continuity mistake: When Suki goes to leave the lift on floor 500, her arms are by her sides, then suddenly both hands are gripping the strap on her bag. (00:14:00)
Continuity mistake: Partway through the episode, there's a wide shot of London, with an undamaged Big Ben visible. The inciting incident of the previous episode was a spaceship crashing into the clock tower, severely damaging it. (00:25:40)
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.