After Hal Jordan went mad, killing most of the Green Lantern
and Guardians of the Universe, the last surviving Guardian formed a new Green Lantern
ring and went to Earth in search of a replacement. Appearing in an alley and finding two men, one of whom was a drunken bum,
he chose to give it to the other, a struggling artist named Kyle Rayner.
Kyle became the new Green Lantern, fought Hal as Parallax,
and went on to join first the New Titans and then the Justice League. When he first met the Flash, they were immediately
hostile toward each other. Wally thought Kyle was an amateur, and Kyle thought Wally was arrogant. As Kyle developed his skills,
and Wally realized he actually had skills, the animosity faded, and after working together in the JLA they’ve
actually become friends—but they remain extremely competitive.