User blog comment:DCFreak22/Mount Justice Authorized Guest Designations?/@comment-24.87.48.133-20120306025220

"You've actually met" that probably means someone with a speaking role, so perhaps Garth or Tula...? In the comics both were superheroes.

"Though in a way you've already met" that probably means someone whom appeared before Humanity (assuming that they're given designations in order of getting into the cave, and also assuming that it's Zatanna's first time) and probably hasn't spoken, or perhaps only one line. Maybe one of the kids in M'gann's and Conner's high school? Mal Duncan, Karen Beecher?