Martha and Lionel to get it on and Clark to walk in on them...

Yup! and then the ensuing scene where Clark goes scurrying over to Lex and says: "Lex, I know we've had our differences, but you have to help me BREAK OUR PARENTS UP!" And Lex is intrigued but noncommital and waits to see what Clark will offer in exchange...:)

FWIW, complicat has been compiling a bunch of lists over on her journal similar to yours and the ones you suggest. Maybe you've already seen them, but if not, they're great reading!