Dos Equis-pert
A person who knows a lot about beer, particularly a certain kind of beer. Often also a connoisseur.
Steve: Dude! Bob just told me how many calories, grams of fat, and percent daily value of vitamin D that a bottle of Dos Equis has, without even looking at the label!
John: What a Dos Equis-pert!
John: What a Dos Equis-pert!