Nightmare at 20,000 Feet - S5-E3
Revealing mistake: At one point, when the gremlin is about to rip open part of the engine, you can see he has a white sole on his foot, part of the costume.
Other mistake: When McNulty uses the stopwatch to rob a bank, he goes through a small wooden door and past the employees. With time frozen, the small door should have stayed open but immediately swings shut.
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.
Continuity mistake: After McNulty freezes the office, a co-worker is getting water from a faucet, and the water is frozen in motion, but right before McNulty unfreezes the office, a female co-worker is in the background at the faucet with no water coming out of the faucet.
Living Doll - S5-E6
Continuity mistake: After Erich takes Talky Tina back out of the trash can and pulls her from the burlap bag, the doll's left arm is pointing straight up above its head. When the shot cuts to a different angle, the arm is suddenly down at Tina's side, even though Erich didn't move it. (00:20:30)
Living Doll - S5-E6
Continuity mistake: When Erich falls downstairs, Talky Tina flies off of the stairs too, yet in the next shot she's shown still rolling downstairs. (00:23:25)
Living Doll - S5-E6
Visible crew/equipment: The boom mike shadow is visible above Annabelle, after she tells Christie that Linda is at the door.
Living Doll - S5-E6
Continuity mistake: When Erich throws Talky Tina across the room, when she hits the floor, her arms and hair change position between shots.
Living Doll - S5-E6
Continuity mistake: When Christie walks up the path, from the car, with her mother, the package she holds swaps arms between shots.
Living Doll - S5-E6
Visible crew/equipment: When Talky Tina calls Erich, the camera zooms in as Erich starts talking - and its shadow appears on his arm.
Probe 7 - Over and Out - S5-E9
Factual error: Cook draws his sun and planets in the sand, saying that it's "my galaxy." When Norda draws hers, he calls it another galaxy. Wrong. He's drawn a solar system, not a galaxy. (A galaxy is a collection of millions of solar systems.) The terms are in no way synonymous - there's a vast difference, and a trained astronaut would definitely know that. Their little ships can't possibly cross galactic voids (that would require tens of thousands of years, even at many times the speed of light), so Cook and Norda's planets are in different star systems in the same galaxy - this one. (00:16:30)
A Short Drink from a Certain Fountain - S5-E11
Continuity mistake: When Raymond arrives to check on Harmon, Flora is sitting at the breakfast bar opening the morning paper. She's holding it straight up in front of her, but when the shot reverses angles, the paper is suddenly lying flat on the bar. (00:16:15)
Continuity mistake: After Oliver hits the bicyclist, the bike's front wheel is turned upright, but is still intact, and the boy has been thrown across a lawn to the edge of a phone booth. In the next shot, however, the wheel is suddenly crumpled, and the unconscious boy has somehow moved to a completely different place on the grass, several feet away from the phone booth. (00:01:00)
Other mistake: When Lillian calls Oliver, she tells him that the car stalled at 3rd and Park - the original scene of the accident. Later, when Oliver goes into his garage in the middle of the night, the car turns on its radio and goes to a news broadcast about the hit-and-run that took place at 3rd and Elm.
Continuity mistake: At the beginning, The main character is driving a car and hits a bicyclist and kills him. The inside shots from the car show the driver's window closed. The outside shots show the driver's window open.
Black Leather Jackets - S5-E18
Revealing mistake: The aliens cause a power fluctuation, and Mr. Tillman complains that all the lights in his house are flickering on and off. But the lamps in his living room are burning steadily. The "flickering" light is originating from what is obviously stage lighting above the set. (00:05:15)
From Agnes - With Love - S5-E20
Character mistake: Using a Texas Instruments TI-89 Titanium, the seventeenth root of 9,000,355,126,606 is 5.781163783, which means the first prime number greater is seven.
Deliberate mistake: The first of two twists meant to come at the end of this episode was the revelation that the mysterious dark rider chasing Anne was herself - 25 years in the future. According to writer Richard Matheson, the director chose, for some bizarre reason, to deliberately spoil this "reveal" by inserting a close-up of the rider early on, showing the viewers who she was at the outset.
An Occurrence at Owl Creek Bridge - S5-E22
Continuity mistake: After crawling from the water onto the shore, the Southerner lies on his back with his shirt gaping open, exposing his entire chest. But in the next shot, his shirt has fastened itself, completely covering his chest again. (00:16:00)
Continuity mistake: When Phyllis stumbles back toward the window, both its draperies are neatly in place. Next shot, just before she crashes through the glass, the drapes are suddenly half pulled down and a broken curtain rod that wasn't there seconds before hangs down over the window. (00:23:15)
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.