Giselle Smith, of Neptune’s moon Triton, had the ability to control her own body metabolism, accelerating it to gain temporarily increased speed, strength and agility, or suspending it to induce a hibernatory state. When alien destroyers attacked Triton, Giselle aided the Legion of Super-Heroes in defence. Invisible Kid developed a crush on Giselle. Giselle rebuffed invitations to join the Legion.
Sometime later, the formation of the UP Young Heroes was announced, with Giselle – now ‘Gazelle’ – among its members. Created as a more ‘manageable’ version of the Legion, the UPYH rapidly came unstuck when their undertrained and mostly inadequately-powered members were sent into situations beyond their abilities. Gazelle became quickly disillusioned with the UPYH, and successfully applied for Legion membership.