When Dr. McCoy sees the rabbit for the first time, the rabbit is clearly seen walking around like a human. However, when he is later examining the rabbit's footprints with Kirk, the footprints are seen side by side, as if the rabbit was hopping, not walking.
As Kirk and Spock run back to the glade they run by the same spot twice. After the aircraft attempts to strafe them, they get up and can be seen running by a crevice in the rock wall that ends with a fork at the bottom and a small boulder on the ground in front of the wall. They then run by the samurai and the camera pan stops on the same crevice even though they had run at least 30-40 yards from right to left.
When Finnegan throws the captain over his shoulder the captain is seen lying on the ground with his shirt intact. But in the very next scene his shirt is somehow ripped with no explanation.
After Captain Kirk's last fight with Finnegan, Kirk's shirt is torn, and his right nipple is totally shown. In the next scene, when the Caretaker appears, Kirk's shirt is somehow tied up to cover up the nipple, something that probably was done to avoid censorship concerns.
After Kirk has "beat the tar out of Finnegan," Spock, standing in the gully below, asks him if he enjoyed it. Spock's next four headshots are obviously in a studio with a painted background, evidenced as well by the lack of background noise. In the next shot, he is back in the gully with Kirk.
Before Yeoman Barrows changes into the "damsel in distress" gown, her uniform is very torn on her right side (from "Don Juan"), but when she changes out of the dress and back into her uniform, her uniform is only slightly torn and on her left side. Still later when she is standing at attention with Sulu and Rodriguez (and for the remainder of the show) her uniform is completely in tact. Correction: The left side of her uniform is tucked into the collar, which is partially torn and hanging over her shoulder - though, given the nature of the planet they are on, one can assume that, in reality, the staff of the planet should have repaired the uniform for her while she was wearing the other dress.
After Sulu fires the pistol, he rubs the barrel, clearly appreciating the object. After firing the barrel would be extremely hot and impossible to touch bare-handed without severe pain being caused. But the "park" they're in would very likely have safeguards to prevent this, unrestrained by the usual laws of physics.
Throughout the episode, several plants and trees are spray painted red. Or it could be alien plant coloration.
William Shatner is three years older than Shirley Bonne. Her character, Ruth, allegedly exactly as she did 15 years earlier, meaning the 23 year-old Kirk had an affair with a 35 year-old woman. However, as Kirk has a reputation for chasing anything in a skirt, it would not be entirely out of character for him.
While on a planet thought to be absent of any fauna, (~12:20 remastered version) a small building with a thatched roof and chimney can briefly be seen in the background while Kirk and McCoy converse as they follow the rabbit tracks.
When Spock beams down to the planet, his boots are already dusty, indicating that he'd been walking around before moving to his spot for filming.
At the beginning of the story, while McCoy reports that there is no animal life on the planet, he and Sulu walk back and forth by a log that is obviously mechanically cut.
When they first see the plane strafing on the one wing when it banks can be seen an AMERICAN air force marking, yet when they get the close up there is a JAPANESE red sun visible on the same plane.
When Sulu and Kirk walk around, they have multiple shadows, revealing the scenes were shot using artificial light.
When Spock is being beamed down, dust spots on the overlay film can be seen as he materializes.
In several scenes, a highway barrier fence is visible in the background.
Tire tracks are clearly visible when Kirk is running after Finnegan.
When Finnegan is yelling at Kirk from the rocks you can tell it was recorded inside some hollow area because of the echo his yells created.
After Finnegan flips and knocks Kirk out, Kirk awakens, rolls over and the next shot, on Finnegan, reveals the shadow of a crew member moving and then disappearing from the left side of the screen.
After Mr. Spock beams down and speaks to Kirk and Sulu, the three of them walk away from the camera in a medium-to-long shot. Just before the scene cuts away from them, bluish puffs of smoke (probably from a crew member smoking) can be seen issuing from the lower left side of the screen.
When Captain Kirk is telling the crew to stand at attention, then the Caretaker appears and the captain moves to the left towards him. As he passes the large tree the boom microphone throws a shadow on it.
Toward the end of the episode, as Kirk is chasing Finnegan, a shadow from the camera crane can be seen in the lower right of the frame tracking along with Finnegan as he runs to the left and then stays in position.
The tiger wears a chain around its neck, which does not fit the story context.
The planet was supposed to be devoid of animal life, yet during the captain's communication with Spock, Kirk is buzzed by a fly.
Although the planet is said to be devoid of insects, during Kirk's first encounter with Ruth a small fly can be seen flitting around her face during one of her closeups.
The planet is reported to be devoid of insects. However, when Tonia Barrows discovers the princess gown at 21:36 a white butterfly is showing.
Despite the fact that the planet is supposed to be uninhabited, no one seems surprised that there are roads running all through the area.
When Kirk and the Yeoman beam to the planet, Kirk goes looking for McCoy. He could have been beamed directly to McCoy's location.
Kirk races through the wilderness, desperately looking and calling for Sulu, when he could simply call Sulu on his communicator.
When Kirk and the Yeoman beam to the planet, they are beamed in between 2 trees that are close together, instead of to a more open area.
The crew is not able to use their communication devices or their phasers but yet somehow Spock's tricorder works.
When Sulu sees someone being transported from the Enterprise, he says, "Someone's beaming down from the bridge." In this series, all transports originated from the Transporter Room; also, he wouldn't know from what duty station someone was assigned.
Kirk tells McCoy, "You follow the rabbit, I'll backtrack the girl, we'll meet up beyond those rocks", doesn't make sense at all. The rabbit and Alice are on the same path, so following that trail in opposite directions wouldn't lead to an intersection.
When Kirk first beams down, he addresses Angela Martine as "Teller". This scene, however, is not included in all syndicated versions.
Since the Enterprise is a research vessel and it has explored space and experienced unusual phenomena on many planets, it sure takes the landing party crew a long time to figure out that the things happening might be created by aliens.
When Kirk notices Ruth, the tiger can be heard growling in the background, even though it shouldn't be in this scene at all.