Revealing mistake: As Sgt. Cain and Chief Lain stand by Marjorie's dead body lying on the hotel bed, discussing her death from an overdose, you can see her stomach rise and fall slightly, though she's supposed to be dead. (00:18:00 - 00:20:00)
Plot hole: I believe in the very first episode, during the flashback when Mick remembers rescuing Beth and killing Coraline, we see him stab her with a wooden stake, which is supposed to paralyze a vampire, as said in the "Dr. Feel Good" episode. However when Mick looks back with Beth in his arms, Coraline suddenly gets up and watches him leave while burning to "death." This is simply not possible; in the "Dr. Feel Good" episode, Mick could not release the stake himself and asked Beth to do it. This also happened in the episode when Josef was staked by the hit man that was hired to kill him, (in the episode where we meet the woman, Sarah I believe, that he accidentally put into a coma after attempting to turn her). Again, Josef was unable to remove the stake himself and Mick had to do it for him, so there is absolutely no way Coraline would be watching Mick and Beth leave; she would still be on the ground possibly burning to death.
The Gloaming - S1-E6
Continuity mistake: When we first see the guy in the tunnel, he runs to the left in the first shot. The next time we see him, he runs to the right.
Factual error: Constantine's driving licence is shown - it's a UK licence, but no. 7 where his signature should be is blank, and no. 8 where his full address should be simply says "England, United Kingdom." Both are printed onto the licence when it's issued - without that info it would never be issued in the first place. And it's not a fake, because why would he have a fake licence with his real information on it? It's just an incomplete prop.
Continuity mistake: Ruth Deaver is helping Alan Pangborn put on his tie. The camera is facing Ruth's back and we see Alan's face in the mirror. The camera then switches angles to face Alan's back and Ruth's face. Alan's collar which was popped straight up from the first angle is now perfectly down over his newly tied tie from the second angle. (00:24:55)
Continuity mistake: When Josh has got out and they go looking for him, they find Aiden on a small bridge. From a distance he's got a very dark sweat stain on his shirt. In a closer shot it's faded to nearly nothing, and gets lighter/darker in different shots throughout the scene.
Other mistake: There is a countdown on the movie screen. It is then reflected in Dusty's glasses. But the numbers are not reversed in the glasses. (00:41:00)
Continuity mistake: When Manx gets in The Wraith and drives off, the car is parked further from the convenience store than before. This is evident by the store's fuel pumps being considerably closer, and not seen in previous shots of the car.
Deliberate mistake: Identical twins Beverly and Elliot have the exact same beauty mark on their faces, roughly on the smile line directly across from the right nostril. Identical twins don't share features like that.
Royal Jelly - S2-E1
Plot hole: It's all very well for Albert to humm "bzz-bzz" to indicate that he has been eating too much Royal Jelly and is no longer entirely human. But "bzz" is just the noise of bees flying, it's not a sound that they deliberately produce. It makes no sense to SAY "bzz." Suppose he was turning into a horse instead, then he might say "Whinny!", but he wouldn't say "Clip clop clip clop."
Audio problem: When Jake is researching how much Good Guy dolls sell for on his laptop, you can hear a phantom mouse-clicking sound, even though he's not using a mouse.
Continuity mistake: When Eden confronts Kinsey by the lockers, as the angle changes so does Kinsey's arm. In some shots, she has her arms crossed and the locker door is closed, in some shots she has one arm up, holding the (open) locker door.
Factual error: The British Army soldiers are not wearing British Army uniforms or carrying British Army weapons and some of them have beards, which are not permitted to British Army soldiers.
Deux Amours - S1-E5
Continuity mistake: Daryl fights the walker on the ship after it kills the other prisoner. He gets backed into a corner and jumps off the boat just as the explosions are happening. The walker he was fighting disappears.
Hear Today, Gone Tomorrow/Double Whammy/Autopsy Turvy - S1-E13
Continuity mistake: Double Whammy: When Lumpy dumps the fishbowl of water on Flippy, his papers fall face down on the floor. A few seconds later, they are face up, and they change position as well. (00:09:37)
Factual error: Sir John Franklin, Francis Crozier and James Fitzjames all wear a crown over an anchor on their epaulettes, the rank badge for a captain with over three years in rank. This is correct for Franklin and Crozier, but Fitzjames only held the rank of commander, and should therefore only be wearing an anchor on his epaulettes.
Plot hole: The powerful 'amulet of protection' makes the bullets strike the shooters instead of John. Clearly it works not just against magic and other ethereal threats, but also against physical attacks. So why does he almost get knocked over by a car? True, he isn't seriously injured, but he was thrown to the ground. The amulet should have pulverised that car or bounced it at least two blocks away.
Continuity mistake: As Rick is getting informed about the CRM's future plans, he is holding his knife under the table. The next shot shows his hand on the table, before showing his hand holding the knife under the table again. (00:23:50)
Continuity mistake: When Randi is in her tent working on her thesis, the computer is on. When something hits the tent, she almost drops her computer which now has a black screen, indicating that it is off. When the werewolf rips through the tent, the computer is now back on.
Continuity mistake: "The Feverman": Before putting the chain around his neck, the doctor removes both his detachable collar and his black string tie. A few shots later, not only is the collar back, but he's now wearing a red ascot-style tie. Both collar and tie vanish again one shot later. (00:17:05)