Source: First seen in Superman's Pal, Jimmy Olsen #48 (1960)
Over the course of the Silver Age, they would suit up again to help various members of the Superman Family. Superman even eventually fit an exit hatch in the bottle for easier access, and anyone could join, not just black-haired young men. In the post-Crisis DCU, a Kandorian Emergency Squad patrolled the bottle city, but did manage to help Superman out on at least one case. And of course, Grant Morrison couldn't help himself; he had to use them in All-Star Superman.