The Legion of Super Heroes is the supergroup that takes anyone. I've been pestering my comic store guy for years about how Bouncing Boy got in when a prospective member must be chosen among a number of applicants. Who did he beat out - The Cardboard Kid?
The Legion has a restriction of one active member per planet. All you need to do is prove your abilities are useful in some capacity, AND be better at using them than any other schmuck from your planet with the same powers. (As I understand it, in the 31st century, every planet is home to a different power set) However, I think exceptions are made for individuals whose powers aren't derived from their planet of origin.
They DID take Maggot...
For some reason, the Legion didn't take Flaccid Lad. Their loss.