Other mistake: In first episode Wells apologizes for locking up Clarke's dad, then acts surprised when she tells him he got executed, when in episode 3 it's revealed they both assisted in the execution.
Revealing mistake: At the river to cross over to Mt Weather, the vine used to swing across the river is just a standard rope, camouflaged. You can see it best when Finn recovers it after Jasper has jumped.
Murphy's Law - S1-E4
Continuity mistake: When Clarke and Finn are undressing in the bunker, right after Clarke takes her shirt off in a closer shot they both have bare shoulders. In the following shot Finn has his shirt on once again before pulling it over his head. (00:39:30)
Contents Under Pressure - S1-E7
Continuity mistake: When Clarke extracts the knife from Finn's chest, suddenly they all get thrown to the ground. Once she stands up again, in the first shot she's holding the knife with the blade pointing behind her, as it was when she extracted it, but in the following shot the blade is pointing forward instead. (00:14:20)
Continuity mistake: When Clarke gets in Finn's tent with Raven to check on his wound you can see the cut running vertically on his chest, but during the whole previous episode the wound was horizontal. (00:06:35)
Revealing mistake: When the guard slices Shumway's wrist, you can see blood coming from behind the glass shard instead of from Shumway's skin.
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)
Factual error: Bellamy tries to fire his assault rifle twice, but because of a dud round, it fails both times. There is an audible click each time he tries. The first attempt there would be a click, because the firing pin was charged when the last round was ejected. However, without that charge either automatically when a round is ejected or manually pulling the charging handle, the second attempt would have been silent since the firing pin was not engaged. (00:35:45)
We Are Grounders: Part 2 - S1-E13
Factual error: After the Arc goes to earth, the chancellor is sitting in a floating ring in space that no longer has any centrifugal motion. He should be floating, but he is seated and gravity is apparent.
Continuity mistake: At the beginning of the episode as Clarke is walking towards the window in the door, her right arm is already injured, but she doesn't actually get that injury until she breaks the window and reaches through the glass, which cuts her right arm.
Continuity mistake: When Charlie is climbing down the cliff the rope comes undone from the tree stump, but a few seconds later you see it still tied to the stump. (00:12:00 - 00:12:45)
Continuity mistake: During the fight between Anya and Clarke in front of the drop ship they are both covered in grime, and after Anya hits Clarke with the log Clarke's face becomes increasingly smeared with blood. Throughout the scene, you can see Clarke's face switch between grimy and bloodied at least a couple times, most noticeably in the shot just after Anya tackles her into the ground and the following one. (00:34:25)
Continuity mistake: When Clarke gives Lexa Anya's braid, we see Lexa accepting it with her left hand and then holding it with both. The next time she's on screen, though, you can see her holding it in one hand, still withdrawing from Clarke. In the following shot, she has the braid in both hands once again. (00:29:10)
Blood Must Have Blood: Part 2 - S2-E16
Continuity mistake: In the scene when Octavia and Maya enter the mess hall while trying to escape the guards chasing them, you can see Maya is walking in front of Octavia. In the shot immediately after, though, Octavia is the one in front and she is being stopped by a guard pointing a gun at her. In the following shot we are back to Maya walking in front still trying to cross the hall, just as she sees guards appear from around the corner; that is the point when the two turn around, and we are once again presented with the same shot of the guard intercepting Octavia, only from a different angle. (00:26:40)
Blood Must Have Blood: Part 2 - S2-E16
Revealing mistake: When Octavia storms into the lab where the Mountain Men have been holding the Ark's people, she has her sword in her right hand. As soon as Kane speaks she makes to sheath it, and we hear the sound we're used to expect to accompany that motion, but you can see she's just holding the unsheathed sword behind her. Then she proceeds to drop it, hiding part of the action from the camera with her body, and although you don't see her catch it again that is made evident from the way she eases the sword on the floor beside her right foot a moment later. Furthermore, in the next shot her sword is not in its sheath. (00:30:05)
Continuity mistake: In one shot when Jasper is unconscious under the table there's a cup on his chest. But in the next shot when Bellamy and Monty go to get him up the cup is suddenly gone. (00:09:00)
Continuity mistake: In the very first scene when we enter Clarke's room from outside the window, you can see bars/old window frames in it. In the next shot, from inside the room, you can plainly see that it looks like an open balcony without any of the previous structures. (00:01:15)
Continuity mistake: When Lexa enters the throne room for the meeting with the ambassadors from the 12 clans, after she reaches her throne she stands in front of it, holding her hands behind her back. In the following shots, her hands keep switching from behind her to in front of her, to at her sides. (00:03:45)
Continuity mistake: At the very beginning of the duel scene you can see Roan extract his mother's sword from the sheath a guard is holding for him, then turn around and step towards the center of the arena. Several seconds later, in the shot of Lexa right after Clarke's arrival, you can see him in the background unsheathing the sword once again. (00:28:00)
Continuity mistake: At the very beginning of the duel scene, Roan starts running towards Lexa holding his sword in his left hand. In the following shot he can be seen running with the sword in his right hand, while when they finally collide he's back to holding it with his left. (00:28:25)
