In Superman: The Movie, in his initial interview with Lois, Superman admits that he can see through anything but lead. It seems pretty clear that she puts that in her article, so it's immediately public knowledge. (I've always thought that was a pretty stupid move on his part, even though I like the "Pink!" part.)

What about in L&C? Is it public knowledge that Superman can't see through lead? How often does it come up in the show? When Superman makes his rude crack about Lois's robe needing to be lead-lined, it's obvious that she knows what he's talking about, but is that one more thing about him that she's keeping quiet?