Other mistake: When Superman pulls off the vault door and places it flat against the wall, it begins to fall back and he holds it back. He then leaves and the door is suddenly propped against the wall.
The Dog Who Knew Superman - S2-E9
Other mistake: A gangster pushes a dog into a well and the dog can be heard splashing around. The man's wife is furious and several people are unable to retrieve the dog. Superman tunnels into the ground and into the bottom of the well and emerges holding the dog. Both he and the dog are completely dry.