They say the clothes make the man. Sometimes, actually, it's the hat that makes the man. This is never more true than when that man wants to get "pimped out."
In real life, no one really knows whether it's a requirement for a pimp to wear a fun and flashy hat. Maybe it would be helpful for identification purposes, but it's not likely to be all that practical. In the world of make-believe, however, the right pimp hat is absolutely crucial to a good pimp costume, whether it's sequined or purple with a feather or has a leopard print.