Many scenes in the color seasons show Clark Kent leaving an office in the Daily Planet building to transform into Superman. When leaving, Kent often wears or grabs his hat, but whenever he approaches the storeroom to change costume, he doesn't have the hat with him.
Many times when Superman gets stabbed with a knife or spear, they show the blade bending over and collapsing. No person would have the strength to forcibly push such a weapon against a hard surface to bend the steel blade, it should just stop against Superman's chest.
With the switch to more expensive color film in 1954, there was a mandate to shoot no more new effects scenes than absolutely necessary. Most Superman-in-flight footage was filmed right-to-left. When the plot unavoidably required Superman to fly in the opposite direction, the footage was "flipped," as can be detected by the reversal of the "S" chest emblem. Another explanation is that George Reeves' "body pan' was attached to a pole that was blocked from view by his body. Unfortunately it was attached on only on his right side. If he had to be shown flying in the opposite direction the film had to be reversed. This not only occurred in the colour episodes, but the black and white ones as well.
When Superman is flying and angles down towards the ground, the clouds stay parallel to his body.
In the opening of the color episodes, as the train passes by, you can see cars and trucks on the adjacent road, driving on the left hand side.
In a few episodes where Superman takes off to fly, the springboard (where George Reeves jumps from) can be spotted at the bottom of the screen.
In the opening sequence at the beginning of all episodes, the revolver that is shown (as the narrator says, "Faster than a speeding bullet.") is obviously loaded with blanks. If there were real bullets in the gun, the lead bullet noses would be clearly visible sticking out in the cylinder. But there are none showing--just dark cylinder chambers. This can be most easily seen if one records the episode and then slows it down or freezes it just as the gun is pointing toward the viewer.
In a few episodes, Superman hits criminals when fighting. From what we know, he has 'super strength' power and that would likely kill or badly injure them. However, some 'Superman' incarnations have him being able to 'control' his type of power and that's likely what he's doing.
No person ever realizes that Superman and Clark Kent are the same person (e.g. from the face, the only difference is one has eyeglasses, the other doesn't) but this is a common cliche in 'Superman' incarnations by its artistic license.
In some episodes, Superman uses a flamethrower (or leaf burner) to burn things or a fire extinguisher to put out fires. Though in the comics (or other Superman incarnations) he has the powers of heat vision or super (sometimes ice) breath that could solve it. It's likely the writers of the episodes were unaware of these powers.
In the opening credits the crowd is looking up in into the sky and four of them say (one line each): "It's a bird (male voice). It's a plane (female voice). It's Superman (male voice)." However, none of the people in the crowd actually can be seen saying these lines.
In some shots where Superman used the springboard to leap out of frame, the tip of the springboard would bounce back up and appear at the very bottom of the frame.
Although a newspaper establishment, The Daily Planet seems to have a great deal of power. In "Jet Ace", a rival reporter accused the
Planet as having "special privileges." Clark Kent is allowed to be present at crime scenes, during police interrogations, busts, and is openly shared confidential information.
Even if Clark Kent's eyeglasses were somewhat 'super' or 'magic' to disguise himself from being Superman. However, in a few episodes, Lois and/or Jimmy see him without glasses (but in civilian clothes) and still recognize him as Clark Kent. It's as if the 'Super suit' makes him be recognized as Superman.
When Clark Kent is about to enter the store room at the Daily Planet, to change into Superman, he always checks to see if anyone is looking, but then before entering the room he removes his eye glasses and loosens his tie which would certainly catch peoples attention and ask questions.