If I could pick any episode? How about every single one in the first two seasons? It seems to me that, in every episode, there was at least one moment when Lois almost figured it out, or just missed a huge clue or...

I just think that could be fun to explore. laugh

Lois: You know, I have a funny feeling that you didn't tell me your biggest secret.

Clark: Well, just to put your little mind at ease, Lois, you're right.
Ides of Metropolis