You can purchase Mardi Gras costumes for adults at Target. If you want additional options, please see the following webiste for more information: www.purecostumes.com/
There are a huge number of stores both online and in the "real world" which sell Mardi Gras party supplies. It would be helpful for you to make a list of what constitutes for you "essential" Mardi Gras equipment and work from there. One can look for specialist fancy dress retailers who often have costumes and accessories which are suitable for a Mardi Gras party. If one is looking for specific Mardi Gras food, one can often find this in a supermarket or delicatessen shop.
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Wearing costumes is a traditions for Mardi Gras. They are worn anytime. People also wear masks on Mardi Gras. Masks are worn during the parade and sometimes during the Mardi Gras ball.
This site is probably a good first stop: http://www.mardigrascostumes.com/ but there are many others which are equally sensible; http://www.costumecraze.com/Mardi-Gras.html and http://www.buycostumes.com/browse/Adult-Costumes/Mardi-Gras/_/N-3iZ27/results1.aspx are two.
Either they're drunk, feeling loose since it's Mardi Gras, they think Mardi Gras is only for adults, guys ask them to so they do it to impress them and get beads, or all of these factors combined.
A krewe is a group of people that make costumes for the New Orleans Mardi Gras Parade.
Mardi Gras occurs in February. The date is different every year and offers parades costumes, beads, a lot of alcohol, and masks.
This link, http://www.meijer.com/s/mardi-gras/halloween-holiday-costumes-accessories/_/N-1z13n9fZ6c2?cmpid=CASEM will take you right to a large selection of fabulous Mardi Gras ideas. You have the option to purchase all of the accessories as well as the entire costume.
Mardi gras
the JESTER is the Mardi Gras mascot.
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There is a website called "Mardi Gras Outlet" which sells masks of all descriptions. Costumes and decorations are also sold here, as well as items suitable for celebrating St. Patrick's Day.