You gotta be either crazy or really tough to participate in today’s Cupid’s Undie Run in your skivvies. It’s bound to be freezing cold, so the faster you can complete the 1-mile-ish run, the better off you’ll be. The event serves as a charity event too, raising money for the Children’s Tumor Foundation. The party gets going at noon at the South Side in Tremont. Runners step off at 2:30 p.m. and the party continues until 4. Registration is $55. (Niesel)