That's just part of Clark. His funny/ornery little quips.
It's also part of what Lois needs in him (and I think wants, too, although perhaps not consciously to begin with). Can you imagine what that ego would be like without Clark to bring her down a peg or two? Well, we don't have to imagine - that's how she got the tag Mad Dog Lane back at the Planet.
Lois needed Clark to prick her ego now and then. He did it in a way that wasn't mean, but was effective in making her think about how she behaved and what she said and constantly challenged her perceptions of herself. And she was the better person for it.
LabRat
