Factual error: When McNulty clicks his stopwatch the helicopter is shown frozen in flight but the blades are shown as a blur, they should be just as much in focus as the rest of the helicopter.
Will the Real Martian Please Stand Up - S2-E28
Continuity mistake: During the scene in the diner between Ross the Martian and Haley the Venusian, there are objects such as a napkin dispenser visible on the counter over the left arm of Haley, which then disappear in the shots over Ross' right arm.
Factual error: The baseball field is said to be in Hoboken, New Jersey, but palm trees are visible outside the ballpark at the beginning of the episode.
Revealing mistake: In the window there are already broken areas where the glass gets broken when Captain hits it. On the bottom pane the grill on the top, bottom and right have a crack before the Captain even hits it. (00:19:00)
Continuity mistake: Block 6 looks to have a no cardboard over the window beside the "Block 6" sign. Then later on they have cardboard there. (00:12:20 - 00:14:55)
Continuity mistake: The Block 6 door is closed all throughout the video, then when Captain runs towards the door it's opened. (00:07:55 - 00:14:55)
Continuity mistake: Becker is standing on the porch at "Block 6" and there are no handrails. When we return to Becker he is in the center of the square area and in the background handrails are there. (00:07:55)
Continuity mistake: The captain goes to "Block 6" which we see is the 1st floor with stairs which are in line with the porch, but when he leaves the stairs go off at a 90 degree angle from the porch. (00:04:50 - 00:06:20)
Continuity mistake: Hunnicut puts a cigar on the bar rail when going to talk to a couple, but during the opening narration in the same spot, it's missing.
Audio problem: When Markie is finally revealing to Helen who she is, Terry Burnham (Markie) is standing behind Janice Rule (Helen) talking to her over her shoulder and can be seen mouthing Janice's lines along with her in between her own.
A Passage for Trumpet - S1-E32
Audio problem: When Joey steps in front of the truck, a lady screams and it shows a close-up of her face. It pans out to a wider shot and for a moment, you can still hear the scream, but the woman's mouth is closed.
Factual error: Decker is flying a Nieuport 28, which entered service in early 1918. However, the date is supposed to be March 5, 1917. Furthermore, the Nieuport was a French-built aircraft that was flown by the French and Americans but not the Royal Flying Corps.
Factual error: Decker speaks of Georges Guynemer's disappearance. Decker believes the date is March 5, 1917, but Guynemer disappeared on Sept. 11, 1917.
Continuity mistake: When Mr. Ferguson is measuring the wax figures, he's shown holding a tape measure up against the figure of Landru (the one holding the rope). In the next shot, the figure is shown with no one near it. The next shot again shows Mr. Ferguson measuring the figure. (00:45:35)
The Last Rites of Jeff Myrtlebank - S3-E23
Continuity mistake: An entire piece of toast disappears off of Pa's plate from one shot to the next. (00:08:40)
Revealing mistake: When Lanser goes below deck frantically trying to find people and tell them to leave the ship, when he opens the door at end of the corridor, it's a bit too obvious that the hallway behind that door is nothing more then just a painting.
Revealing mistake: When all of the neighborhood children push Bevis's car for him, one of them looks directly into the camera.
A Nice Place to Visit - S1-E28
Revealing mistake: When Valentine tries to shoot Pip, he shoots the lamp to see if his gun works. The lamp breaks a full second after he shoots it. It was obviously done by special effects.
A Thing About Machines - S2-E4
Revealing mistake: When the electric razor is coming down the stairs after Finchley, the wire used to pull it is visible. (00:19:50)
Answer: It's explained in the episode. The aliens are experimenting to see how humans react to various scenarios. This just happens to involve them using super strength.
Thanks. It's been a long time since I saw the episode so I forgot.