An annual winter tradition in cities all over the country since 2010, Cupid’s Undie Run gears up (or down, as the case may be) for the Boston edition on February 17. This fundraiser to help combat neurofibromatosis, a condition that causes tumors to grow on nerves throughout a person's body, starts locally at noon at Irish-themed pub The Lansdowne in the Fenway. From there, barely-clad participants set out at 2 p.m. on a mile run through the neighborhood before returning to the warming indoors to dance and party with a pint or two until 4 p.m. Only registered participants are allowed inside the venue, yet spectators are encouraged to line the course to cheer on the runners as they streak down the avenues around venerable Fenway Park.