Deliberate mistake: When Jack is scanning the gas mask people, he has a scanner on his right wrist. However, when he shows Rose and the Doctor his image of the Chula warship, the scanner is on his left wrist. The makers flipped the stretch of film, according to the commentary, to make the shot work. (00:37:45)
The Doctor Dances (2) - S1-E10
Continuity mistake: When the Doctor is looking at Rose's hands, turning them over repeatedly, while she's describing how she was hanging from a barrage balloon, there's one moment where her hands are turned palm-up in a shot facing her, but back-up in a shot facing him. (00:18:25)
The Doctor Dances (2) - S1-E10
Factual error: Magnetic tape recorders weren't available outside of Germany during World War II. True the tape recorder could have been captured from the Germans, but, as it was cutting-edge technology for 1941, it would hardly be likely to have ended up in a hospital office.
The Doctor Dances (2) - S1-E10
Factual error: Look closely at some of the freight wagons at 'Limehouse Green' railway station: several of them appear to have 'British Rail Freightliner' livery. This episode is set in 1941, but British Rail did not exist until 1948, and the Freightliner Division did not exist until the 1980s.
Revealing mistake: The 'earthquake' that takes place in this episode results in CGI-created cracks in the pavement that are very unconvincing. They do not appear to displace anything and - in a related continuity error - the cracks disappear in shots taken from ground level (the cracks are only visible in high-level 'looking down' shots). (00:34:30)
Factual error: Emergency Service vehicles in Cardiff (indeed, throughout Wales) have their signs in bilingual English/Welsh. So the police cars and ambulances seen in this episode should have 'Heddlu'/'Police' and 'Ambwlance'/'Ambulance' bilingual logos. However, the police car seen after the earthquake has its label in Welsh only. (00:40:33)
Audio problem: Just after the Doctor makes his appearance and Lynda tells him he's "in the house", she appears to continue talking to him but we never hear what she says; instead the scene cuts to the other two housemates complaining about the Doctor's sudden appearance. (00:01:40)
Continuity mistake: When the Doctor and the housemates in the Big Brother house are watching TV, the brand name of the TV - Sony - appears in some wide shots, but is absent in other wide shots and all close-ups. (00:14:10)
Continuity mistake: As the Doctor, Captain Jack and Lynda with a Y have been captured, the Doctor turns his head to the right, then after it cuts it shows him turning his head again and saying "Let's do it." (00:32:05)
Continuity mistake: Just after they break out of the prison cell, you see Lynda reach for her gadgets twice. (00:32:20)
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)
Other mistake: After Jack uses Davitch's information to complete the Controller's coordinates, the Doctor uses a remote to project a holographic, transparent screen of the location in question. The image shows Orion's Horsehead and Flame Nebulae. In a shot immediately afterwards, looking through the holo-screen back at the Doctor and company as he explains what's going on, the image of the nebulae is not mirror-reversed as it should be, but is the same orientation as in the previous shot. The kicker is that the image of the nebulae has been altered, as well: it's already been mirror-reversed - in the actual sky, the Flame is left of the Horsehead. (00:38:40)
Factual error: The Doctor claims the Daleks are hiding themselves from sonar. But sonar relies on sound waves, which can't travel through the vacuum of space. (00:38:45)
Revealing mistake: After the Doctor deactivates the signal hiding the Dalek fleet, when the camera zooms out to show the ships, the background image of the Horsehead and Flame Nebulae is cut off a bit below where the Dalek Emperor's flagship is shown, revealing the end of the picture they used for a background. (00:39:00)
The Parting of the Ways (2) - S1-E13
Continuity mistake: Near the beginning of the episode, the Doctor and Jack destroy a Dalek who is inside the TARDIS. It is seen again later when the Doctor, Rose and Jack come back into the TARDIS after talking with the Dalek Emperor. Yet later when the Doctor is sending Rose home, there is no destroyed Dalek. (00:14:20)
The Parting of the Ways (2) - S1-E13
Continuity mistake: At the beginning of the scene where Rose, Jackie and Mickey are in the restaurant, in the wide shot, Rose moves her left hand to the side of her head, while looking down with her head facing towards the other side of the table, which her elbow is resting on. In a close-up immediately afterwards, she's looking out the window with her hand to her face and her elbow resting on the windowsill. (00:18:50)
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.