I experienced 3 Mardi Gras. The closet thing to it i had ever experienced was when the bulls were winning championships in the 90's. The whole city is out, drinking, dancing and having a great time.
Find a good parking spot and say goodbye to your car for a week. You wont be able to drive anywhere. And FYI "Fat Tuesday" is really an 8 or 9 day event. Each day it gets crazier and crazier leading up to the big parade.
Rex waiving to me on St.Charles: