Bobby Gill, one of the co-founders of the Cupid’s Undie Run: “The other co-founder, Brandon [Hanrahan], actually came up with this idea back in January of 2010, a little bit after New Year’s. And our friend Chad, his little brother has this disease called Neurofibromatosis (NF). Basically, NF causes tumors to grow throughout the body at this alarming rate, and causes deafness, blindness, paralysis, and severe pain; it’s this terrible debilitating disorder. So, we knew we wanted to do something for the Children’s Tumor Foundation, but we wanted to make as big as an impact as possible. So, you know, we were, like, ‘We are going do a 5k [run], and we are going to do a happy hour. No, no, no, let’s do something that’s truly crazy. Let’s do an underwear run in the middle of the winter.’ And so we did it that first year. We thought that, maybe we get 30 to 50 people, maybe we’ll raise $2,000. We ended up having 650 people and we raised $10,000 that first year. Since then, we are now in 18 cities throughout the world. Sydney, Australia jumped on board this year, so that was our first international expansion. And as of this morning, we have raised $1,000,000 for the Children’s Tumor Foundation for this year’s run. We couldn’t be happier with how things have gone. It’s truly incredible.”

Gallery • 44 Photos

Take a dip. Runners celebrate post-run.