Other mistake: Old Ben duplicates Jenny so she can accompany him to his home planet. As he can turn into anything, he should be able to approximate her height. When the now twins walk out, the girl on the right is a couple of inches taller than the girl on the left.
Continuity mistake: Rance McGrew's white horse is tied up with its head just a few inches from the hitching rail, but a moment later is untied and several feet away from the rail. Next shot, it's tied up close again, though no one's touched it. Finally, it's completely loose, and at the episode's end, is wandering into the street. (00:22:00 - 00:23:30)
Other mistake: Chambers asks what time it is on Earth, a strangely vague question to which the Kanamits grant an equally odd answer: on Earth, it is noon. It can't be noon everywhere on Earth at once. While it can be fancifully explained away ("They somehow knew to answer for the time zone he was taken from"), it still jars the viewer, because neither Chambers nor the aliens, both highly intelligent, should make this sort of imprecise mistake. Both director Richard Bare and Damon Knight, author of the original short story, confirmed this as a scriptwriting error that should have been caught before shooting began. (00:02:15)
Continuity mistake: The events shown are supposed to take place at almost exactly midnight, yet when Conny goes to the graveyard the sky is bright and everything is well lit, much brighter than moonlight. Just as he enters the graveyard there is an abrupt change in lighting and the scene is suddenly much darker.
Continuity mistake: The car Rance drives onto the set can be seen in the street from inside the saloon, but disappears when Rance, in character, comes through the swinging doors. It's visible again in the very next shot, but vanishes anew when Jesse James comes through the doors, after which it yet again reappears in the very next shot. (00:04:30 - 00:07:20)
Continuity mistake: Richards opens the door and finds a lion on the bed over his wife's body. When the door first opens, the corpse has dark hair and the blanket is twisted and disarrayed. But when the shot cuts to the lion leaping, the corpse's hair is a lighter color and the blanket is neatly spread across the bed. (00:23:40)
Factual error: Author Damon Knight was happy with Rod Serling's TV adaptation of his short story - except for the change that allowed the humans to translate the Kanamit language as though it were a code. Said Knight, "Without some sort of interplanetary Rosetta Stone, deciphering an unknown language would be impossible." (00:22:10)
Factual error: As well as the obvious problem with translating an unknown language as if it was a code, there is no chance that the word "serve" would have the same double meaning in English and Kanamit. It would be like the word "dope" and its French equivalent meaning "idiot" and "illegal drugs" in both languages.
Factual error: Throughout this episode, the TV western supposedly being filmed lacks several essential elements. There are no clapboards to mark the scenes; the modern-day car is constantly in shot through the swinging doors; and the set is located inside the "real" saloon when it should be on a sound stage.
Visible crew/equipment: After the two travellers have paid for their gas, when Frisby advises them to check in someplace because of the clouds, the reflection of the moving boom pole and mic can be seen above the word "shop" on the store window. (00:08:00)
Visible crew/equipment: When Frisby tells the two travellers that they're looking at the grandad of the American automobile, we can see the reflection of a crewmember wearing a suit, possibly the director, who stands up from a directors chair (also seen in a following shot). Then as Frisby tries to locate the gas tank, the shadow of the moving boom mic is visible on the store's doors. (00:06:20)