Continuity mistake: When Clara takes Rigsy's chronolock, in the closeup of the tattoo Clara's lifting her hair with her right hand and showing the tattoo with her left hand, but in the next front-facing shot her hands have switched, she's holding up her hair with her left hand and showing the tattoo with her right hand. (00:26:45)
Continuity mistake: At the beginning, Missy is using a knife to sharpen a stick to a point. Later in the scene, when she says to Clara that if they go rescue the Doctor, everything the Daleks can throw at them is between them and him, she lists only the stick among their assets. The knife is never seen or mentioned again after Missy was done with it. (00:04:18)
Factual error: The Viking village has tubs of electric eels in the boathouse, which prove instrumental to the plot as the power source of the makeshift electromagnet used to relieve several of the attacking aliens of their helmets. The problem is that the Vikings live somewhere in northern Europe, and this episode takes place in the 800s. Electric eels are native to the Amazon and Orinoco rivers of South America, which at this point in history no one in Europe knew existed.
Other mistake: The Doctor says "These are a sort of mark 2, yeah?" The subtitles say "These are a sort of Mach 2, yeah?" (00:17:40)
Other mistake: O'Donnell imitates another character retching. The subtitles show this as (WRETCHES). (00:03:00)
Other mistake: Prentis says "In my ship, I have directions to my planet and a selection of items that you can oppress me with." The subtitles say "[...] appraise me with." (00:06:25)
Continuity mistake: After Missy hooks Clara up to the Dalek armour, she takes her hands away from Clara's temples. However, in shots facing her for the next several shots until she stands up and backs away, her arms are still raised. (00:22:24)
The Magician's Apprentice - S9-E2
Continuity mistake: During the exchange where the Doctor says "You flatter me" and Davros responds "A pity. I intended to accuse", Davros' hand goes from just under his chin to resting on his chair's control panel. (00:40:15)
Continuity mistake: When the Doctor hands out of the base manuals to the expedition crew for the dream test, Albert Smith is shown with his manual open in shots from behind him several shots before he's shown opening it in a shot facing him. (00:35:56)
The Magician's Apprentice - S9-E2
Continuity mistake: When Colony Sarff arrives at the arena, he's seen unclasping his hands twice, in the close-up and following wide shot. (00:28:38)
Heaven Sent - S9-E12
Continuity mistake: When the Doctor is first shown discovering the word "bird" written in the sand on the floor of the teleport chamber, the handwriting changes from being somewhat messy in the wide shot to being perfectly neat in the close-up.
Continuity mistake: Rassilon's gauntlet is supposed to be exactly the same one he had in "The End of Time", but the design has changed. Most noticeably, the user's palm is now uncovered.
Continuity mistake: When Bonnie is filming the transformation of the Zygon man who she stripped of control over his shape, her grip on the phone she's using changes between shots.
Continuity mistake: When Bonnie throws the laptop with the Osgoods' message to the floor and stomps on it, the computer's position changes between shots - take note of the tape markings on the floor. In addition, the position of the plastic frame of the laptop's screen changes: in the first shot, it's mostly popped out, but in the second shot, it's mostly attached.
Continuity mistake: When Bonnie gets a video call from the Doctor, her grip on the phone changes between shots.
Continuity mistake: For most of the robbery sequence at the beginning, the Nightmare (a disguised Ashildr) is holding her pistol in her right hand. When she's yelling at the Doctor for interfering with her robbery while he's looking at the chest strapped to the back of the carriage, however, she's holding it in her left hand. It switches back to her right after the carriage escapes.
Deliberate mistake: In real life, Viking helmets didn't have horns on them, because it would be a liability in combat. The horns were actually for drinking. The Vikings in this episode were given horns anyway, because the writers didn't feel it was worth having to include an explanation of hornless helmets to a general audience.
Continuity mistake: When the Doctor is listing questions about what exactly the ghosts are, he goes from gesturing with his left hand in the close-up to gesturing with his right in the wide shot. (00:17:17)
Audio problem: Shortly after arriving at the Drum and taking shelter in the Faraday cage, when the Doctor is looking out the window in the door at the ghosts, he says "What are you?" His jaw doesn't move.
Continuity mistake: When the Shade leaves Clara and she falls, her body is twisted because of the way her legs are bent with one on top of the other and her arms are out to the side. In the overhead shot of her, her positioning has changed, her body isn't twisted and her arms are more straight down her side.
Chosen answer: No, no information is avalible for the identity of the entity.