One traditional drink on St. Patrick's Day is a Black & Tan, a mixture of a dark stout and a lighter ale. The trick to a Black & Tan is in the pour. Do it incorrectly, and you'll end up with the beers totally mixed. Do it correctly, and you'll get a layered drink that's ready to drink after you raise your glass and say, "Sláinte!"
I love this Black & Tan instructional video from Hop Talk because it's visually appealing and the music is perfect. As you can see, making a Black & Tan isn't difficult, you just have to take your time.