Why do people pinch each other on St. Patrick's Day?
As you probably learned the hard way in middle school, those who don't wear green on St. Patrick's Day are eligible for pinches that range from flirtatious to malicious. One reason for this is that the holiday is about taking pride in one's Irish heritage, and the potential pinch encourages people to be bold about their Irishness. The second reason is leprechauns. The mischevious mythical creatures are rumored to pinch those aren't wearing green, but their non-existence makes it far more likely that you'll be pinched by an 11-year-old with a cruel streak.
Why do people drink on St. Patrick's Day?
As you know, folks who've so much as seen an Irish person on TV celebrate the holiday by drinking. This tradition has surprisingly innocent origins. During the original Feast Day-iteration of St. Paddy's, restrictions from Lent were cast aside and the day had a general atmosphere of indulgence -- that's the point of a feast after all. So, people ate and drank as much as their religiously observant hearts desired, though often this didn't involve beer. By law, pubs in Ireland had to shut down on the holiday for most of the 20th Century, and drinking on the holiday was generally considered a bad look until the late '70s. Then beer advertising made a big push to link drinking and the holiday for obvious reasons, and this marketing effort, along with some unfortunate stereotypes, are the reason you'll either be in hiding on Saturday or having a very un-festive Sunday.