Revealing mistake: When the Capri crashes into the goal net & they go to arrest the suspect you can see sky satellite dishes on the houses in front of them. Satellite TV didn't start in the UK until the 80s.
Revealing mistake: In the scene after the fire, when Kyle is playing with a candle, as he picks up the candle his belly button is visible. It has been established that Kyle has no belly button, therefore this is a mistake.
Children of Earth: Day One - S3-E1
Revealing mistake: When the children are possessed by the 456, they're supposed to be frozen and stare blankly ahead. But during the second possession, as the camera is panning across a school playground, a boy on the far right is looking directly at it. As it moves closer to him, he swivels his eyes back to where they're supposed to be. (00:16:30)
Revealing mistake: The money that Micah dumps out of his backpack is very obviously fake. In fact, the $20 bills have Benjamin Franklin's portrait on them.
Revealing mistake: When Dexter is retrieving a blood sample after cutting Benny Gomez's cheek, there is no blood in the dropper and he puts no blood on the actual slide. (00:49:50)
Revealing mistake: When we first see the army of Starks outside Global Dynamics, it's quite obvious that only one of them is actually the actor that plays Stark; the others are merely people who look similar.
Revealing mistake: After Betty leaves Jodie the voicemail, when Betty looks at Henry's Facebook page with the intention of unfriending him, she moves the cursor to the "remove friend" tab. Then in Betty's closeup we see that tab's reflections on both lenses of her eyeglasses, but the problem is the reflections are not backwards. (00:33:35)