Sapphire Stagg is the love interest of Metamorpho and his alter ego, Rex Mason from the Justice League episode, Metamorphosis. She is the daughter of industrialist, Simon Stagg. She first met Rex Mason through the employment at her father's company. Their relationship is kept a secret. She is first seen while John Stewart, the Green Lantern while Rex Mason allowed John to visit his apartment. Simon decides to pay a visit to his daughter's apartment, and Sapphire tells her dad that she is going to go with Rex. However, after Rex was transformed into a multicolored mutant while clearing his desk to go home, she becomes horrified at the hospital. After Mason gained a battle with Superman, Batman, Hawkgirl and J'onn J'onzz, she calls John and tells him the latest and John reassures her and also realizes that Rex has followed his career avidly. While Sapphire is watching the news of a huge creature defeating the Justice League, a giant monster grabs her and climbs up the side of a tall skyscraper as Rex helps the Justice League to save her. Mason tries to rescue her, but the monster is too powerful and John rescues her before Rex sacrifices himself against the monster in order to save Sapphire and the Justice League. Sapphire was sadden about his death, fortenately, Rex survives the explosion after one of her tears fell into a puddle of the chemical and rises from the ground. Sapphire was happy to see that Rex survived and the two hug each other for Rex's victory as John and Hawkgirl see the two happy couple hugging together.