Downton Abbey is, in a sense, a bit like meth: highly addictive, but most of us don't know why. As far as the TV show goes, it might just be that we all feel very very fancy and classy while watching it. And thus it lends itself perfectly to a droll drinking game:
Take a drink of Pimm's every time you call the show Downtown Abbey.
Sip a Campari and orange juice any time Thomas and/or O'Brien do something nefarious to set up Bates.
Enjoy a glass of red wine whenever Mrs Patmore chastises Daisy. (Take a second drink when it's done unfairly.)
Sample a good cognac whenever somebody mentions it's time for Mary to get married.
Imbibe an Old Fashioned whenever a Crawley sister backstabs or talks dirt about any of the other sisters.
Down a Scotch any time you exclaim words that could be taken straight from the show. Examples: "Scandalous!" and "What a scollywop!". Take a second drink if you say it in a British accent.
Sample a fine porter whenever Mr Carson eavesdrops on someone's conversation.
Drink a Drambuie if you're watching the first season on Netflix and you wonder why Laura Linney is introducing Masterpiece Classics.
Finish a bottle, any bottle, all the bottles, if you can come up with a good reason for why you're watching the show.