Usually, student council runs it. It's a riot. We do it during the week of homecoming. Every day that week, we have a dress up day, and on Thursday, the day of Powder Puff, we have switch day, so all the students can get involved.
Girls dress like guys, and guys like girls.
Like I said, it's a riot. Any club could do that, really, though. The girls borrowed football jerseys from the guys, and some of the smaller guys even borrowed cheerleader's uniforms. We did ours during the last part of the school day, and it ended when it was time to go home. Organization isn't hard.