When the crew lands in the year 1947 at an American production facility for radio and furniture cabinets, a huge object is seen in the background. It is covered by a large, seamless plastic sheet, and held down from the wind with lumber. Polyurethane plastic sheeting had not yet been developed: in nineteen-fifty-three, a catalyst was found and applied, and new plastics such as sheet form were developed, and became common. The unknown object was most probably hidden as it did not relate to the time and location sensitivity of the town portrayed.
When the two men are discussing "Voltones" while holding Smith and Will, the Robot approaches. One of the men shoots the Robot, striking him just to the right of the illuminated voice-plate leaving a sizable mark. Seconds later, after the Robot has incapacitated the men there is no mark whatsoever.
Close-ups of the Jupiter 2 shortly after it lands on Earth are shown with a rotating radar/satellite dish on the top of the ship. Minutes before when the ship was shown just before touch-down, no such dish is visible.
After coming out of hyper space John, Don and Dr. Smith look out at planet Earth from inside the J2. Also visible is Saturn, Jupiter and some other planets and/or moons in our solar system. Not all of these other planets would be visible to the naked eye simultaneously as shown.
After passing through an anomaly of time and space, the Jupiter II arrives in Earth orbit - 50 years in the Robinsons' past. It is made clear that the family cannot remain on the planet, but there is no discussion about how the Jupiter II will return to its original time and place. At the end of the episode, the ship simply flies away from the Earth of 1947.
Judy Robinson's hairdo changes just after the Jupiter II lands - notably when she is captured by Craig, it is now shoulder-length and straight, but before landing, her hairstyle is curlier. It resumes its curly aspect after John and Don rescue her - without comment or explanation.