I've always thought that the show missed a golden opportunity by not bringing back Linda Gaye Scott. In the first season, she played "Moth", the moll of the Riddler. Now, if you know Batgirl's comic book history, you know that they very first supervillain she ever faced was Killer Moth (a man). But how wonderful would it have been if Linda had come back on the show in the third season, this time as Killer Moth, and she was a nemesis for Batgirl? Heck, if the proposed Batgirl spin-off had been picked up, Moth could have been a recurring villainess there.
(I think it's worth pointing out that Linda rocked the shiny purple lamé suit a full year before Yvonne did, and filled it just as magnificently.)