Who says taking the train is boring? January 12th was "no pants" day on the public transit system. It's a prank started by Charlie Todd's Improv Everywhere. There really isn't a point to it and it's not a protest against anything. Well, perhaps they are protesting pants or celebrating legs? Anyway, you can see half naked people on the train in the Today Show clip above and another news report below the fold. Technically, it's not illegal unless you don't wear undies, then you are just a flasher. Also, it looks like it's only happening in the cities, so don't try this in small town America (if you can find a bus there). They'll think you're crazy.
[Source: Today Show, YouTube]