Snapper Carr was an honorary member of the Justice League of America when the comic first begin its run, in the early 60's. Snapper Carr had no superpowers, and was an all-American teen, although he had a penchant for using beatnik slang. He joined the JLA through the good fortune of being the only person in the town of Happy Harbor not to be brainwashed by a gigantic, celestial starfish in one of the JLA's first cases. Being an honorary member, he attended meetings and, when the writers needed a plot device, helped with cases. Although he looked and had the mores of what we would think of as a preppy, well-behaved teen, he talked in ridicuously exagerrated beatnik lingo.
The writers of the comic included Snapper Carr so that the youths of the era would have someone to identify with in the series that was a normal kid. I don't know how normal Snapper Carr was, even by the standards of the comic book geeks of the time, but readers identifying with him was probably not a big factor in the success of the JLA amongst readers. He does, however, provide some interesting comic relief, as well as a demonstration of what comic book editors would think a beatnik kid would talk like.