Continuity mistake: Both the positive and negative versions of Lazarus have a long mustache and a fairly full "waterfall" beard - until the scene in the briefing room, when inexplicably, the mustache and beard are both suddenly so thin they're barely visible. As soon as they beam down to the planet, however, the much thicker facial hair is restored. (00:23:00 - 00:24:30)Jean G
Continuity mistake: During the attack on the outpost, as Spock arrives in his foxhole, Kirk puts down the box of ammunition and positions the grenade launcher. We cut to a higher angle as Spock scrambles around to the Captain's left, and Kirk is putting the box down and positioning the launcher all over again. As the action was supposedly continuous, there wasn't time for Kirk to pick the items up and set them down a second time. (00:08:40)Jean G
Continuity mistake: The lawgivers' robes that Kirk and Spock take off and drop on the floor just inside the doorway disappear after they phaser the wall to reveal Landru. The robes reappear a few minutes later, but have now migrated several feet to one side, bunched up against the wall where they are no longer in tripping range of the actors about to enter the scene. (00:42:25 - 00:45:00)Jean G
Revealing mistake: When Kirk finds his position on the bridge occupied by the Tribbles, he calls for Dr. McCoy, and as he arrives, Kirk thrusts some of the Tribbles under his nose. In the shots where Kirk's face is seen, one of the Tribbles he is holding features a visible seam.
Continuity mistake: Kirk is holding three large tribbles while talking to Uhura on the bridge. After McCoy enters, the tribbles keep changing positions in Kirk's hands as the shots cut back and forth. (One on top and two underneath, then two on top, etc.). (00:31:45)Jean G
Continuity mistake: After his initial mind meld with the horta, Spock tells Kirk, "That's all I got, Captain: waves and waves of searing pain." A minute later, he says that it's "a highly intelligent, extremely sophisticated animal" that calls itself a horta. Apparently, waves of searing pain were not all that he got after all. Unlike Spock to be so imprecise.Jean G
Revealing mistake: Stock footage strikes again when Kirk orders the red alert. A shot of the bridge and view screen, with Kirk standing in front of his chair, once more switches Kirk out for a stand in, and Chekhov has gone and is replaced by what looks like from behind like a young woman or a man with a long neck. Also the central display between navigator and helm is now different from that earlier. (00:11:15)Jean G
Continuity mistake: After partially healing him, Gem falls away from McCoy and lands, unconscious, perpendicular to the dais he's lying on. When Kirk and Spock rush over, however, she's suddenly moved several feet away and is now lying parallel to the dais. (00:44:50 - 00:45:35)Jean G
Continuity mistake: McCoy uses a "masking device" to block out the bridge personnel's heartbeats. When McCoy masks Spock's heartbeat, he holds the microphone, err, masking device over the wrong part of Spock's anatomy. We'd already established that Spock's heart wasn't in the same place as a human.Jean G
Continuity mistake: When the landing party beams over at the beginning, the transporting officer is wearing a blue jumpsuit, but when they go to the closeup of his hands, they have a red uniform, two braid stripes, and are the standard shot they use when Scotty does the transporting.