The one that is most prevalant to me is the reason the writers of fanfic have adopted as the 'reason' for Lois totally illogical behavior in dating and agreeing to marry Lex in the House of Luthor and Barbarians at The Planet.
The 'fact' that she agreed to his advances and proposal was because she didn't love him and therefore he couldn't hurt her like someone she actually loved could when the relationship fell apart has been picked up and used a lot in many different fics. I don't think this idea was ever really supported in the show beyond Lois admitting that she 'had feelings' for Lex but probably didn't love him. Their explanation was that Lois was taken in by the fact that someone like Lex (at least the person she thought he was)would be interested in her.
Tank (who never bought into the idea since he believes that Lois is really a closet romantic and might have a 'relationship' of convenience with someone she doesn't love, but would never marry them... that was reserved for the 'Prince Charming' she never really believed would come along)
