Revealing mistake: The ghosts often cast shadows.
Suggested correction: You can also hear their footsteps. But I'm not sure this is a mistake, just their own perception. Within the ghostly world they appear and act just like they would in life.
The ghosts are manifestations of energy, therefore they have no physical body to block light. Even if in the ghostly world, physics are physics and there should be no shadows.
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.
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: Multiple times throughout the show, Kimber can be seen in quick shots with light pink hair (the same color as Jem's), when her hair color is actually a dark pink/red color. (02:00:00)
Continuity mistake: The fish that Harley uses to protect herself from the Joker changes shape and size every shot.
Turtles All the Way Down - S1-E13
Other mistake: When Dr. Lee and Dr. Evans are arguing just after Red Reality Michael and Green Reality Michael converse, Michael turns around and says, "Shut up!" but the closed captioning says, "Enough!"
Revealing mistake: During the opening theme, when the children are watching the magician, you can tell they were not actually filmed together. The magician scenes are filmed more professionally using a sharper tape or film image, whereas the children scenes look more like a standard fuzzier film-type such as on a projector (primarily used at that time).
Revealing mistake: In the song "Living Island", we see Judy frog jumping over Pufnstuf. When she goes back down, the wires holding her up and putting her down are visible.
Other mistake: When Teela is at Snake Mountain, she overhears TrapJaw saying how Skeletor's electrical creature will control all of the machines at the palace. When Teela returns to He-Man, she says that the creature Skeletor created is called Byte. There's no way for Teela to know the name of the creature, since TrapJaw never referred to it by name. (00:14:24 - 00:15:20)
Factual error: When Mr Gore destroys the television set, it is obviously a prop, as when he breaks the screen there is no noise, in reality there would be a loud bang as there is a vacuum behind a TV screen of that era.
Continuity mistake: When Marshall first finds Trip's letter, he holds it from the left side. In the close-up, he's holding it from the right side. (00:02:10)
Factual error: When Alina stands outside of the door to the banquet hall, waiting to demonstrate her power to the king and queen, there is a modern electronic occupancy sensor on the wall behind her.
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.
Plane Death - S1-E14
Deliberate mistake: When the bad guy goes to smash a table onto Michael Landon notice the plate of glass in front of him, visible. The glass is there so Landon doesn't get hurt and to make the table break into pieces in front of him.
Gortimer vs. The Mobile of Misfortune - S1-E3
Visible crew/equipment: When Stanley is riding the kart in the race, the shadow of the camera equipment is briefly visible bottom right, just before the kart starts to fall apart.
Coach Fussell's Lament - S2-E5
Continuity mistake: Chairface and Chrome Dome arrive at the Brianchild's house in the same car, but drive off in separate cars.
The Frankenstein Murders - S1-E5
Factual error: When Mary looks at the newspaper, it says "Tuesday, March 31, 1827." But that was a Saturday.
Welcome to Hotel del Luna - S1-E1
Continuity mistake: When the woman on the street greets younger Chan-sung, her right hand is raised slightly when she says "Tell me the year and hour that you were born", but in the next shot, her right hand is suddenly in her basket. (00:13:58)