A street gang in LA and rivals of The Bloods
, another LA gang. They like wearing blue. This is what is known to anyone outside of California.
Apparently they do illegal stuff and frequently send their cronies to Urban Dictionary to 'represent', most likely to the dismay of their even partially literate members.
At some point Quentin Tarantino has mentioned them on The Tonight Show.
Famous rapper Snoop Doggy Dogg claims that that he keeps "a blue flag" in his left back pocket, since that is the "crip side".