Time Out says
For one day each December, the 12 Bars of Xmas pub crawl (better known as TBOX) takes over Wrigleyville, bringing the drunken stupidity of the summer months into the holiday season. More than 40 bars throughout the neighborhood participate in the booze-soaked revelry, as participants in festive garb knock back drinks while indulging in nonsensical traditions like cereal shots and sticker exchanges. While it's a fun day on the town for most, TBOX has a history of violence, property destruction and general debauchery, which explains the heavy security presence. If you must go, be safe and don't do anything dumb.