well, it was a family show, so they kept it pretty clean. I'd say they usually said things like "oh, shoot!" or "crap!" as opposed to actual profanity. In reality, I'd guess Lois swears more freely than Clark, but she wouldn't swear a whole lot. Journalists in general tend to be a group that swear a lot. But I doubt Clark swears much. It would have to be something pretty upsetting. Lois probably swore a lot at one point to prove she was just as tough and hardened as all the men in the newsroom. But by this point she probably wouldn't swear much, I'd think.
Annie
