The turn-of-the-millenium version of Supergirl and the classic Silver Age incarnation meet each other. The Silver Age Maid of Might was retconned out of existence after dying back in the 1980s; this plot has her trying to avoid that fate.
Years earlier, the big-haired, head-banded 80s Girl of Steel met her disco-outfitted 70s self. More on Supergirl's history can be found here. The Supergirl Parade of Fashion may be found here.