People are generally awful. For that, we dedicate one post a week to a situation that enables people to be obnoxious. The best part? These annoying people are universal: they appear in this situation hundreds of times over all across America. If you can't understand why a certain person is on this list, bad news; that's you.
Here are some annoying people on St. Patrick's Day:
The Person Who Is "100% Irish"

100%? Come on, 50% at the most.
America's Irish and Italian populations have a serious problem with this; they constantly describe "how I_________ I am, bro. Seriously, my family landed here on a boat in 1845. That means I was practically born there, dude." Or it means you're American with distant roots in another country. On St. Patrick's Day, these people come out of the woodwork, proclaiming their heritage makes them more "legit" to celebrate on this fabulous day. Relax, man.
The Person Who Can Drink So Much Because They're "100% Irish"

That was whiskey...
Alcohol absorption is affected by several factors, some of which being weight, gender, alcohol consumption experience, and more! But for some reason, people tend to believe that with the right genetics, you can ingest a few gallons of grain alcohol and still perform retina surgery. Wrong! Go ahead, try and drink 18 beers because you're "Irish."
The Person Who Wants To Fight You

I just got here
While there is definitely a stereotype about the Irish getting drunk and fighting (two characteristics they wear with pride, actually), it's SUPER annoying when you're trying to enjoy St. Patrick's Day and some asshole wants your experience to be as genuine as possible, complete with unintelligible slurred speech, bloodshot eyes, and classic Irish anger.
The Person Who Celebrates So Hard

Dave, are you ready to leave. Dave? Shit.
Nothing can ruin a good time quite like going overboard and blowing your load too early, which can easily happen when you get an over-eager person, a holiday, and alcohol together in one room.
The Person Who Bought A Plastic Horn

Not you.
Ok, we can hear you. How much attention does a person need? You're already covered in green from head to toe, do you really need a 4 foot long plastic horn to broadcast your annoying presence?
The Person That Did So Many Car Bombs, Bro

"All for ME?!"
The Irish Car Bomb is one of the greatest concoctions alcohol has ever brought us. Guinness, Bailey's Irish Creme, and Jameson whiskey combine to create a delicious mixture of alcohol that goes pretty much into your body in 2 seconds. But just please enjoy the drink quietly with your friends, we don't really care how many you did, unless you did like 25 of them, because that's pretty amazing.
The Person That Doesn't Plan Ahead

Most of us will enjoy the drunken revelry at a parade. Make sure you understand that being outside isn't like being in a bar; there's not a lot of (legal) bathrooms to be had. Don't go pissing your pants. We saw about 30 people with this problem at the parade last year.