The Annual Santa Skivvies run is kind of like the Castro neighborhood's version of Santa Con - except a little bit more naked. And instead of an all-day block party, it's a race - for a good cause. Participants ditch the Santa suits for their undies - and a Santa hat or antlers, of course. It costs $35 to join the race, but it's FREE to watch! The money goes towards supporting the San Francisco AIDS Foundation, which provides free AIDS testing and care services throughout San Francisco. The run starts at 11 a.m. at The Lookout and loop around the Castro. The entire run spans 1.3 miles, or 2.09 km, so it won't take that long, but there's a gigantic block party afterwards. Check the FAQ page for more info!