Flea is a magician of renowned strength with the ability to create illusions and to charm others.
He appears in Fiendlord's Keep in the Middle Ages, where he is fought as a boss.
Fighting alongside Super Slash and Ozzie, he appears again in Ozzie's Fort as Diva Flea.
In a New Game Plus of Chrono Cross, Flea is battled as a secret boss in the Bend of Time along with Ozzie and Slash. In this fight, Flea's gender symbol is male, although he sports pink hair and a skirt.
Source: Wikia, "http://chrono.wikia.com/wiki/Flea", available under the CC-BY-SA License.