Dr. Smith, Will, and the Robot come upon a jewel-laden crown. When Smith decides to try the crown on, the act unleashes a fury of lightning and Will helps his friend remove the crown. The Robot then says the crown holds no danger for Will. To assure Dr. Smith that the crown is harmless to him, Will dons it. Suddenly, trumpets blast and humanoid aliens appear announcing that the wearer of the crown is to be the king of their home world, Andronica. Though flattered by the offer, Will turns them down. Dr. Smith, however, after sending Will and the Robot on their way, tells the leader of the entourage that he is descended from kings and would make a perfect ruler for their planet and suggests that he be considered. After Dr. Smith departs, the leader, Nexus, transmits a message to his superior, a hairy-faced alien who is a true Andronican—the group that Smith and Will had met were nothing more than human-looking androids made by the Andronican.
Smith becomes king and is shortly to be taken to Andronica. The Robot, however, has detected something sinister about the alien party and submits his findings to the rest of the Robinson Family. It is decided that a rescue attempt is to be made before Smith departs.
The alien intercepts the conversation and decides to solve the problem by making a duplicate Smith and passing it off as the real thing. The new Smith is everything the old Smith was not: hardworking, considerate, inventive, and self-sacrificing. The Robinsons suspect nothing.
However, the real Smith discovers that an Andronican king is no more than a figurehead and is sacrificed and stuffed after his coronation. He manages to escape when the Andronican is knocked unconscious and returns to the Jupiter 2 to the surprise of the rest. When the Andronican androids come to reclaim Smith, the duplicate pretends to be the real Smith and goes off in his place. The Robinsons lament the fate of the duplicate Dr. Smith, but the real Dr. Smith assures them it will be safe; the Andronicans have a great respect for virtue; they only choose the most worthless of beings as their kings to rid the universe of such useless creatures.
- Some may think that this is not one of the best of the first season, but it benefits from the performances of Hagen and, in a dual role, Harris. Hagen had previously appeared on Irwin Allen's "Voyage to the Bottom of the Sea," and would later portray "Inspector Kobick" on the producer's "Land of the Giants." Though most television fans remember him as "Doc Baker" on the long running "Little House on the Prairie" show.This installment comes from the final half of season 1 of the show and it is another example of the change in format from adventure and survival to farce and fantasy.
- Liam Sullivan played the part of the head android-human Andronican named Nexus. Sullivan was born William Edward Sullivan on May 18, 1923 in Jacksonville, Illinois, USA. He died on April 19, 1998 (age 74) in Los Angeles, California, USA.
- Liam Sullivan was one of the few actors to have appeared on both classic Sci -Fi shows "Lost In Space" and "Star Trek". Sullivan played Parmen, in "Plato's Stepchildren" for Star Trek.
- Kevin Hagen played the actual hairy and homely Andronican alien. Hagen was born Donald N. Hagen on April 3, 1928 in Chicago, Illinois, USA. He died on July 9, 2005 (age 77) in Grants Pass, Oregon, USA. Most people will know and recognize Hagen from "Little House On the Prairie, where he played Dr. Hiram Baker (Doc).
- Live coverage of the Gemini VIII splashdown meant that Season 1 Episode 24 "His Majesty Smith" was postponed. CBS received over 2000 calls of complaint that night.
- The exterior of the alien spacecraft in this episode is the same as that used in The Keeper.
- Dr. Smith, Will and the robot expect to find wild truffles on an alien planet. Truffles are an Earth species
- In the background of the Andronican's chamber can be seen the model of the Bubble creature's ship from the 2nd episode, although it is upright. Also returning is the noise made by the Rubberoid - it is used here as the sound effect of a cloning machine.
- The rise of Dr. Smith as the most popular character on LIS is confirmed with this episode, the first to truly center on him.
- This is the first of several times throughout the show that Dr. Smith is either duplicated or has a doppelganger, and the plot of the clone/duplicate sacrificing itself to allow the real Smith to live on is touchingly reused in season 2's "The Phantom Family".
- The sequential lighted ring above the cloning table is the Jupiter 2 lower power unit from the full size model, also used in The Lost Civilization.
- In the scene with the two Dr. Smiths seated next to each other in the control room of the Jupiter 2, the opening in the floor for the ladder is not there.
- Why did one of the Smiths have to leave? I can’t believe people as tender-hearted as the Robinsons would leave either one of them behind on an alien planet all alone.
- If the Robinsons absolutely HAD to chose only one Smith, why wasn’t it Zack? The Doctor may have been there first, but he is lazy and selfish and causes nothing but trouble. Zack was hard working and very kind. He would have made a far better addition to the crew. After all the trouble the real Dr. Smith has caused them it's hard to imagine they would so easily want him back.
- It was suprising to see Doctor Smith's daring escape from the alien ship. Bashing somebody over the head and running away is hardly a normal thing for Doctor Smith to do. Usually he's so inept he just sits there and cries!
- If the Andronicans discover their King is really Zack and they decide not to kill him, what prevents them from coming back to fetch the real Smith again? Obviously traveling from world to world is a quick and easy process for them, so what would hold them back?
- When Will, Smith and the Robot first encounter the Andronicans, the blonde girl to the immediate right of the leader either has a massive case of stage nerves, or is on drugs, as she can't stop shaking during the dialogue. Later, aboard their spaceship, when the Andronicans are suddenly frozen, the same girl now holding a basket cannot stop blinking, and has trouble keeping her hand steady. She's still shaking in the scenes where the Robinsons meet with the newly crowned King Zachary the First [Hey medic!]
- During the opening credits when Will and the Robot approach the camera, once again you can see the mechanical man's tow cable in front of its tracks.
- When Smith breaks a flask over the Andronican leaders head, he turns to run and encounters then throws to the ground what is obviously a dummy model of the Andronican Nexus..
- A duplicate Dr Smith appears in this episode for the first time - this will become an often used plot device in later seasons.
- In the scene where the real Dr Smith escapes, you can see that the alien spaceship appears to be actually embedded in the rock.
- Dr Smith: "King Zachary the First....oh my!"
- Dr Smith: "Then I really am the King?" Alien: "Oh yes. You are the King. For festival of sacrifice." Smith: "Sacrifice?" Alien: "Big Festival. Everybody come. Drink gloog. Make sleemoth"