Ironically, this being the last episode of the series, we finally find out the science behind what causes the effects of Kryptonite on Superman (as explained by Prof. Pepperwinkle's theory of negative and positive Kryptonite charges).
There were plans announced in June of 1959 to do a seventh season of twenty-six new Superman episodes. John Hamilton, who played Perry White, had passed away in the fall of 1958 and they were going to replace him with Pierre Watkins who had played Perry White in the 1940's Superman serials which also starred Noel Neill as Lois Lane. Unfortunately, just a few days after this announcement on June 16, 1959, George Reeves died of a gunshot wound to the head. It was listed as an apparent suicide although there are some who believe he was murdered.
When the burro reads Jimmy's mind to determine his age, we find out that he's 22 years old.
You'll notice that when Superman is talking to the burro and she answers his questions with a "yes" or "no" head gesture, Superman is actually pulling on her harness to force the gesture.
Lois says "With Clark still missing we're a bit shorthanded on this flying burgular story, but "Mr. "Kent's" trying to get ahold of Jimmy, take him off the feature until Clark gets back", It should have been "Mr. White's".
ILLOGICAL: First of all, is it even possible to go down 250 feet of water when you're off a pier that close to shore? And secondly, why didn't Superman react faster to getting them out of the bathysphere the moment the door closed in on them? He actually waited until the thing submerged.
Goof: When the bathosphere sits on the bottom of the harbor, 250 feet below the surface, with Perry White, Jimmy, Lois and Superman you can see Goldfish swimming outside through the window.
This episode marks the final appearance of recurring actor Ben Welden portraying a criminal.
The Mr. McTavish robot costume had been used 4 years earlier as Gorog for the movie The Bowery Boys Meet The Monsters.
You can see the ONLY time that Superman uses his magnetizing powers, via his x-ray vision, in this episode.
When Lois and Jimmy first arrive at Dr. Ladislav's, he warns them that if he whistles, Superman will come to his rescue (fearing that they're kidnappers). Later, while driving through the desert, Ladislav continues to whistle so the three of them will be rescued. Then, when Ladislav finally drinks some water to be able to whistle, Lois asks Ladislav AGAIN why he's whistling, although he explained earlier.
When Superman is suppressing the atomic blast, they couldn't use the stock footage of him flying. So they shot new footage of George in which he is laying on a metal brace. When he flails back and forth you can easily see this. It's a shame they couldn't figure another way to do this as watching George Reeves propped up like this was not at all flattering to him.
GOOF: The sound effects person and editor forgot to add in Superman's landing sound cue when he first arrives at the cube. It just has George hopping in. On this same note, George Reeves' landings from high above camera view have since been abandoned as he aged. In the last season, he would do nothing more than just hop into frame.
If there was ever a belief by any character on the series that Clark Kent was Superman, it was dispelled in this episode when he becomes the two Supermen. One becomes Clark Kent in his hotel room and the other a jailed Superman.
George Reeves himself had earlier played a Knight of the Round Table in the 1949 movie serial The Adventures of Sir Galahad.
This is the only episode in the series where we get to see Superman fly in something other than his costume.
At the beginning of the episode when Superman arrives to save Jimmy from Gannis, it's obvious that he swung in on the pole when he lands.
Mr. Zero refers back to the episode Panic in the Sky , saying Martians have admired Superman ever since he saved Earth from an asteroid.
While Mr. Zero is talking to Georgie and Slouchy back at their hideout, he points at both of them (although it's natural human gesturing from the actor) but they don't freeze.
During the ride to the Queen's tomb, Jimmy reveals that Lois is 26 years old.