One time my sister and I were walking down into lower Manhattan from Central Park (and I was in new shoes... that was fun).
Suddenly, we find ourselves unable to keep going, because this huge "parade" was going on. But it was pretty much the least organized parade ever. It was like every single NYU student, New School student, etc. had all decide to paint their bodies and wear crazy costumes, etc. The floats were pretty much just built onto Pickup Trucks (and they were freaking AMAZING, because that's what happens when a bunch of college-age art students get to make floats that aren't for marketing purposes).
Also, a whole crapton of naked/half-naked (noteworthy because "half-naked" doesn't really mean what we're used to here).
And it just kept going and going and going, lol. It turns out this parade wasn't even celebrating anything in particular - student organizations at NY schools just decided they wanted to do it, coordinated with each other, and did it.
Was awesome.