Clark discovers that he is a good singer, so he quits reporting to become a rock star.
Clark discovers that he is the evil twin.
Lois discovers that Ellen Lane is not her biological mother.
Lois discovers that she is not the oldest child - she has an older brother that she never met.
Lucy discovers that Lois is shacking up with Superman, without knowing that Clark is Superman.
Jimmy discovers that Clark is a Very Patient Man, prompting him to pull a 40 Year Old Virgin scenario.