Aside from the "wheel," Carol is definitely my favorite Ferris. Initially appearing as Hal Jordan's employer and love interest in 1959, Carol Ferris would become a Green Lantern supervillain in 1962 when she took on the guise of Star Sapphire. In the current comic continuity, the Star Sapphire's wield violet light (powered by love) and are often at odds with the Green Lantern Corps.
First appearing in 2002 as a member of Luthor's Injustice Gang, Star Sapphire made her onscreen debut on the Justice League animated series. She would continue to aggravate the heroes (even though Hal Jordan was not the Green Lantern in the Justice League continuity) throughout the series run and into Justice League Unlimited.
Carol Ferris would next appear, without any alter ego, in 2008's Justice League: The New Frontier. The movie presented a fairly traditional take on the Hal Jordan origin story in which Carol was seen as Hal's employer and love interest.
Carol would once again (briefly) appear in the 2009 Green Lantern: First Flight origin tale.
In 2011, Star Sapphire will finally return to face off for the first time onscreen against the Green Lantern Hal Jordan on Batman: The Brave and the Bold. In Scorn of the Star Sapphire, she will battle Hal with her own brand of violet ring constructs.
Carol Ferris will also play a lead role in the upcoming Green Lantern live action movie. Although it is unlikely she will become a villain in the movie, her villainous turn has been hinted for potential sequels.
In fact, eagle-eyed viewers have already been able to spot the Star Sapphire symbol on Carol's flight helmet in the Green Lantern trailer.