This is a type of sign language that gangs of juvenile delinquents use as a type of secret communication. Comes from all of those years of spearing things in the jungles and communicating with other spear hunters. (Wait, that requires intelligence). Anyway, it is impossible not to laugh at at, because it looks so hilarious.
"I just make up my own gang gestures when I see those crime-monkeys gesturing at me. They think I'm nuts that way."