Baileys Irish Cream is a popular Irish cream liqueur, made from a blend of (you guessed it) Irish whiskey and cream, as well as vegetable oil that keeps the two from separating, and a number of herbs and sugar for added flavor. According to the manufacturers, Baileys will last for two years after the day it was made, opened or unopened.
Though Baileys markets itself as a classic, it wasn't invented until 1974, when it essentially created the market for Irish cream. Every bottle contains a signature by "R.A. Bailey," who is a completely fabricated person. The name was inspired by Bailey's Hotel in London.