Sheldon is wearing a T-shirt with the superhero Green Lantern's symbol on it. Unlike his other heroes, Green Lantern would seem the most appropriate for Sheldon because Green Lantern's power comes from The Guardians of the Universe, a race of omnipotent beings at the center of the universe, who are immortal. Sheldon would not be able to resist the high intelligence, high discipline and limitless power of these beings.