At Norwescon this year, I was ordering a drink that I decided would be called a third and third and third.
The right way to make it: In a large cocktail shaker, combine equal parts Half&Half and Irish Cream, plus ice. Shake. Pour into a glass. Up, no ice. Basically, you want to mix it and strain it thru the ice to chill it, but you don't want the ice melting in it.
To make it quickly: Dump a handful of ice into a glass, pour in Bailey's until it's about half full, top off with half&half. Stir with a straw. Drink.
edit: And yes, I realize that it is, in fact, a half and quarter and quarter. STFU.