Everyone who knows about Mardi Gras probably automatically thinks of carnival masks and Mardi Gras beads (and partial nudity) when the festival is mentioned. For the last century these rituals have been interlaced with the history and traditions of the Mardi Gras celebration in such a way as to make them permanently related by this point. At the same time, not many people are conscious of what the beads mean, or their history, or why they are shouting out strange phrases to get them.
At some point people may be told the story of Rex Krewe throwing out the original Mardi Gras beads in the early 1900s, made from cheap glass trinkets imported from Czechoslovakia. This event drew such attention that it was quickly adopted by the other krewes, and enhanced by adding unique doubloons and other trinkets to attract revelers and partygoers of all stripes to their floats. The classic bead colors actually have symbolism behind them: gold signifies power, green represents faith, and purple is justice.
Trading those gold, green and purple beads for quick glimpses of female nudity, however, have very different origins. This particular ritual is probably as widely known as the beads themselves, but it actually has nothing to do with the original traditions of Mardi Gras in New Orleans. Instead it is a byproduct of very drunk partiers, and is actually kept primarily to the French Quarter rather than the entire city. Many people in New Orleans would just as soon see that particular tradition die out, and soon.