Continuity mistake: A few moments after Pike and his group leave the room because they didn't find prisoners, Octavia pulls her own head out of the hole and says "all clear." Then she pulls two machine guns out of the hole with both hands and puts those guns on the left and right sides of the hole separately. In the next shot, those two guns aren't in the same position. Both are in front of the hole near each other. (00:28:58)
Continuity mistake: Toward the end John Murphy gets a collar around his neck. In subsequent shots the lock on the collar is alternately locked / open. (00:34:00 - 00:35:00)
Continuity mistake: During the funeral on the oil rig, right after Octavia collapses under the effect of the drug, Clarke has a sturdy, simple metal cup in her hand, but in the following shot we see her dropping a completely different, clay-like and more elaborate cup that shatters when it hits the floor. (00:39:40)
Continuity mistake: While Clarke and Lexa are kissing, Clarke removes the neck strap of Lexa's blouse. In a subsequent shot of them kissing, the strap is back on. It disappears again as they move towards the bed.
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: When going to retrieve Murphy from the dropship, after Bellamy subdues his sister, his gag is covering his mouth. Then, as Pike moves towards him, suddenly it's magically not. (00:22:20)
Continuity mistake: In the opening scene while Lexa and Clarke are talking, Lexa's shoulder guard keeps shifting on her shoulder from one shot to the next, as does her red sash. (00:01:20)
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: When Clark is drawing Lexa, a dot between her eyebrows turns darker and then changes into a gold star. (00:01:40)
Continuity mistake: During the duel scene Lexa's face gets smeared with black blood following a few hits, but in the shot when she announces "The Queen is dead" right after she kills Nia, Lexa's face is suddenly clean. (00:30:55)
Continuity mistake: During the duel scene, after Lexa smacks Roan flat to the ground, he lands with his right hand right upon one of the swords. In the following shots, the sword changes position and can be seen at various distances further to his right. (00:30:10)
Continuity mistake: At the beginning of the duel scene, when Roan and Lexa lock swords, they do so with each sword pointing to their holders' right. During the shot of Lexa being forced to her knees while Roan tells her to get down, though, both swords are pointing to their holders' left, and Roan can be seen holding his with his right hand instead of his left like he does in the rest of the scene. (00:28:40)
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)
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)
