Ever since I was born on Halloween, I've enjoyed a good costume party. I usually start planning in August, lying on a hot sunny beach, what I'll wear that chilly night in late October. Today, though, I have a more urgent costume concern-what to wear for the 95th annual ING Bay to Breakers foot race, this Sunday, May 21.

As much a party as a competition, the 12K (7.46-mile) event draws roughly 70,000 runners and walkers who cross San Francisco, heading west in a steady stream of athletic determination mixed with kooky wigs, masks, Elvis outfits, high heels, flip flops, body paint, floats, and for a small (and presumably chilly) contingent, birthday suits. The official 12K National Championship event must be the zaniest race recognized by the USA Track & Field Association, and the only ambulatory carnival that can qualify American runners for the Olympic trials if their race times are fast enough.