Helen Slater, who once was the star of a little movie called Supergirl, will be a guest star on this season of Smallville as Supergirl's aunt...and Superman's Kryptonian mother. Talk about messing with the family line. Unless she were at some point to play Lois Lane, Slater will have played as many female parts in the Superman universe as one person could logically hold down.
In the meantime, for those of you who do not remember Supergirl, it would serve you well to forget it was ever made. A blown-out 80's feature with very little in common with the successful, and often quality, Superman movies of the day, Supergirl starred Slater and Faye Dunaway doing a very early prototype version of Meryl Streep's character from The Devil Wears Prada.
TV Guide.com: On Smallville, Supergirl Is Superman's Momn. Got it?