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.
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.
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.
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.