While you're stuffing your face with corned beef, beer, and/or rye during tomorrow's St. Patrick's Day festivities, remember to sport some green. If not, you might get pinched. (You also might get a sexual harassment lawsuit tossed your way, fellas, so keep your sausage fingers to yourself in the workplace.) Why do we pinch people for not wearing green on St. Patrick's Day? Good question. Here are a few answers we found on the glorious internet:

According to WikiAnswers:

Ireland is known as the Emerald Isle. Green is traditionally worn on St. Patrick's day to honor the Emerald Isle. Tradition holds that on that day, people who do not wear green are pinched as a reminder to wear green to honor the Emerald Isle.

Huh. That's boring. And possibly not accurate. According to the Christian Science Monitor, the tradition or pinching started in the U.S. in the 1700s:

Forgot to wear green on St. Patty’s Day? Don’t be surprised if you get pinched. No surprise, it’s an entirely American tradition that probably started in the early 1700s. St. Patrick’s revelers thought wearing green made one invisible to leprechauns, fairy creatures who would pinch anyone they could see (anyone not wearing green). People began pinching those who didn’t wear green as a reminder that leprechauns would sneak up and pinch green-abstainers.

Oh, we like that answer. Yahoo Answers also agrees that it's a U.S. tradition based in anti-leprechaun sentiment. So, please, remember to wear green tomorrow, folks.

Also, here's a handy list of San Francisco bars participating in St. Patrick's Day merriment.