I'm from New Orleans (or am I??) and it really is just an excuse to get wasted. Basically, you go out and yell at people for beads, dubloons, stuffed animals, flowers, etc. If you can get it, you generally want it. People are drinking and partying... In all honesty, Mardi Gras is a way to sin your heart out before Lent, and another reason to party it up.
The totally awesome thing is that most schools get a week off for Mardi Gras, so it's a pre-spring break. With that being said... Happy Fat Tuesday guys! (a week late, but whatever)