Originally Posted by death-lord
in smallville itself it established that clark could have children (superman returns nod)
Well, Lois and Clark clearly establishes that not only can Clark have children, but his and Lois's children are key to the future. The only way to reconcile this with the end of Season 4 is, Dr. Klein is wrong. And it actually seems that Lois' father figures that out, but then has his memory of such wiped.