In early Superman stories it's explained that Superman's x-ray vision cannot penetrate lead. This is because in the real world X-rays cannot pass through lead or any other material so dense.
In Doctor Who, the original Cybermen are defeated when they are forced to inhale powered gold, which clogs their breathing filters, suffocating them.
Several writers later and we find that Superman cannot affect lead in any way, but has little problem with denser materials. He cannot even heat up this soft metal with his heat vision because... well, for no reason given. We also find that Cybermen are now so allergic to gold that a coin fired from a slingshot will kill them, even though it cannot possibly affect them in the way that originally incapacitated them.
It's all Chinese whispers. Writers see what their predecessors have written and follow the form without considering the concept. And that's without even considering the stuff they change deliberately...