Plot hole: In Episode 1-7: The Serene Squall, the Enterprise is at the edge of Federation space, and it is stated that it would take two days for a message to be received by Starfleet. Later in the episode, they have no problem establishing a real-time connection to Vulcan, which, according to canon, is only 16.5 light years away from Earth.
Plot hole: Owen is unable to give Henry the kiss of life as he has no breath, and yet he is able to talk.
The Tale of the Mystical Mirror - S5-E3
Plot hole: It makes no sense that Ms. Valenti gives all of her employees a compact mirror and also invites them to her home. Any of them could open their mirror while standing near a painting of Ms. Valenti and they would discover the secret, as Cindy does.
Suggested correction: She isn't concerned about employees seeing her true reflection because she was planning to capture three of them at her home anyway and transform them into dogs for the ritual. Presumably, if she had finished the ritual - and she almost did - she would keep her youthful appearance and no longer look older in mirrors.
Suggested correction: The compact mirror includes a palette of cosmetics. Cindy shows it to Laurel, who says, "She gave one to me, too, like we're ever gonna use it." Presumably, the employees are mostly using the free samples of cosmetics from the shop displays. I myself have owned some compacts that I didn't always want in my purse (if they were too big or awkward in a certain purse).
Triumvirate of Terror! - S3-E8
Plot hole: After Superman thwarts Lex's plan and knocks the Kryptonite into the sewers, Lex yells in frustration, splits his power suit off and flies away on a jet pack. Superman just lets him go. Wouldn't Superman chase him and catch him, especially seeing as how weak Lex would be like that? (00:07:35)
Plot hole: Lucien, Trustan and Aurora are somehow compelled to believe they are Mikaelsons, when no-one knew how to compel until Elijah compelled Aurora by mistake when they fled. So when did this supposed compelling happen? Did Elijah go back and do it later on? The siblings all had knowledge of him compelling them, so I'm confused exactly when they all learned of their ability.
Left Behind - S1-E9
Plot hole: It's revealed that Chronos is Mick from the future after he was abandoned by Snart. However, in the episode White Knights (episode 4) the earlier version was able to sneak up on Chronos and surprise him with an attack from behind. If that was a future version of Mick then surely he would have remembered the attack coming and could not have been so easily caught off guard.
'Unmei no sentaku' mitaina - S1-E6
Plot hole: Akito's attack is point blank, on a ship part of a fleet with Distortion Field activated (basically, they have shields, like the good guys' robots). The explosion he causes is according to Ruri's damage report big enough that it managed to vaporize 80% of the ships they were facing, but his Aestivalis and the other 3 right floating nearby make out of it literally without a scratch. (00:05:10)
Plot hole: Kate in the Batcave says with absolute certainty "Alice doesn't know that Bruce Wayne is Batman. Whoever stole the gun, knew that Bruce had to have the suit to test it on." Both statements are leaps in logic with no foundation. Alice knows that Kate is Batwoman, and that Bruce's office is her center of operation (she even shines a bat-signal there!). It would be perfectly logical to assume that she made the connection. The testing bit is simply a non-sequitur; plenty of weapons can be made and tested on armor which fits the specifications, real or inferred, of a particular target, without being in possession of the item as a whole. (00:16:00)
Plot hole: White Base and the interior of Luna II withstand without a scratch the explosion of the thermonuclear reactor from the Magellan from just a few meters, while the blast literally vaporizes the Zaku far away from the entrance and threatens to damage the Musai, hundreds of meters away.
Plot hole: When Frankie tries to get Johnny to chase her out into space, he tells her he can't follow and warns her to turn back due to the thin atmosphere not being able to keep their flame powers active, and indeed her flames die out, and she begins falling back to Earth. However, several minutes later in the episode, both of them are just outside of the Earth when Terrax arrives, and again at the end after she becomes the new herald of Galactus, Johnny follows her into space well beyond Earth before his flames die out. (00:03:15 - 00:06:03)
Plot hole: In the lab when Liz makes the slides of her cheek cells and the cells from Max's pencil, the first time she doesn't add stain and the second time she does. If she's going to be a molecular biologist she really ought to learn to apply techniques consistently. (00:07:30)
Plot hole: The grounder's leader Anya states that the missiles (flares) burned a village to the ground. If this were true, the flares couldn't have flown very far, otherwise that village would have been too far away for the grounders to know about. In a previous episode, when you saw the flares from space, it was obvious the flares traveled hundreds if not thousands of miles away. (00:31:30)
Plot hole: In the end of the episode, Wolverine is seen recuperating after surgery removes the microchip in his brain, and his head is bandaged. Performing invasive surgery on Wolverine's brain isn't possible, since that would require going through his adamantium-infused skull and no conventional material is capable of that. Only a less invasive technique (such as going through the cranial sutres or cranial foramen) would have been effective and that most likely would not have required Wolverine's head to be bandaged (especially with his rapid healing mutant ability).
The Monsters are Due on Maple Street - S1-E22
Plot hole: The street sign in the beginning is all wrong: it faces the camera rather than the street where the story takes place. In a typical American city, street signs are almost always placed in the direction of the street they are indicating, so drivers on the other street in the intersection know what they are turning onto or passing. In other words, the story is not set on Maple Street! Maple Street is the intersecting street at the end of the road the story is set on.
Over My Head - S3-E4
Plot hole: Daphne was able to hurt Duke because his name appears on her cell when he called, but names only show up on a cell phone if the person's number and name are programed into the phone, and Duke has already said he doesn't know her.
The Messiah on Mott Street - S2-E38
Plot hole: No one in Goldman's house finds it at all strange that a mailman arrives at the door with a letter after midnight on Christmas Eve. Nor, a short time later, does the doctor or anyone else passing by at this very odd hour wonder why the same mailman is collecting mail from a street box at dawn on Christmas Day.
Plot hole: In the hoverdrone footage, Peter goes down suddenly during the gunfight, apparently from a wound to either the head or torso. However, there is no wound or blood on him and even his bulletproof vest has no marks except for the normal studs. If he had been hit in an extremity he would not have limply collapsed instantly. Sonrisa's goons are using automatic weapons that should have no trouble hitting him many times from that range of only a few meters. (00:54:00)
Plot hole: Why would Danger Mouse go on the roller coaster at the end without seeing Greenback go on it first? Greenback went first in the ghost train. It also doesn't make sense that Danger Mouse would go on it when Penfold pretty much tells him flat out that it IS a trap.
Plot hole: Sydney is able to surmise from the artwork (we could also say from the writing, but her rival is one step ahead of her for 2/3 of the episode and it is established that he does not know the language) the precise location of the koi in Lumbini. The map is 150 years old, but there's no way even with a big stretch of imagination to buy that they both'd be able to pinpoint with such ease and certainty its location in the basement of a random building in the bustling market center of a town, that surely changed plenty during the past century and that does not bear any special landmark.
Plot hole: When Nadia had been held captive in The Village, how did she get word to her accomplice to be ready at the exact time, in the exact location, and with a packing crate ready, and a whole series of transports arranged? Even if Nadia was in on the ruse of conning Number 6, wouldn't he be suspicious?