Has it been a year already? It seems like only yesterday we were casually observing the annual pantsless BART ride while quietly wondering about the cleanliness of those cloth seats. This weekend, from 1 p.m. to 4 p.m. on Sunday afternoon, the brave and bottomless will once again bring their whimsical flashmob to BART trains and platforms throughout the Bay Area. But listen up, kids, the impromptu (although can we really even call it that anymore?) event has a few more guidelines this year, and there's even a movement to include a couple Muni lines on the action. From the Facebook event page:

THERE WILL BE TWO ROUTES THIS YEAR. We want to spread it out evenly. We will use your last name to divide the groups, if your last name starts with A-M take the first route and if N-Z take the second route. Route 2 is more walking, route 1 is more time on public trans.

Once attendees have figured out how to organize themselves like a kindergarten class, stripped down to their underoos and ridden BART all the way to Montgomery Station the two groups will then split up. The A-Ms will head to Levi Plaza on the 10-Townsend, while the N-Z folks will ride the F-Market along the Embarcadero to the same destination. Of course, since this is a flashmob, you can pretty much do whatever the hell you want, as long as it's the same thing everyone else is doing.

For complete route details and suggest BART boarding times, check the Facebook event page. For up-to-the-moment updates on Sunday, you can follow the group on twitter at @NOPantsSF. And if you just want to look (creep!), there are always photos from previous years. Consider yourselves informed/warned.