I'm not sure if you're familiar with it, but many of the Mardi Gras krewes have a huge party after the parade finishes its route and they call it a Ball. The end of the parade is like the end of a fireworks show where everything goes nuts. Bacchus is one of the big parades, and they roll into a huge arena (it used to be the Superdome for Bacchus, but that was a long time ago).
Check this out - it's pretty cool. Good stuff starts about 35 seconds in.
Not exactly the same thing, but, I participated in the Krewe of Trobadours townhouse ball in Lafayette a few times when I was a kid. My mom was Queen of the ball one year too. I wish I could find the pics. Pretty fond memories of that. The costumes were fascinating.