Fallon, who tapes Late Night at studio 6-B inside 30 Rockefeller Plaza, plays the head of the family, similar to the Earl on Downton Abbey.
The funnyman also enlisted close friends Brooke Shields, Fred Armisen and even show announcer Steve Higgins to take on the roles similar to Lady Grantham, the daughter Edith and Mr. Bates, respectively.
Downton Sixbey episode one, which debuted on Thursday night, runs for more than 8 minutes. The episode takes viewers into the inner workings of the studio, its writers and one's struggle with a Kim Kardashian joke.
Fallon's spoof serves as a good distraction for fans of Downton Abbey, as the show's third season doesn't air for another five months.
In recent months, Downton Abbey has been transformed into several variations including Downton Arby's (starring Richard Kind and Matt Walsh) and a Spike TV commercial on Saturday Night Live. Even the characters have been re-imagined as dogs, thanks to the folks at Dogster.com. The site identifies the Earl as an English Bulldog, Lady Grantham as a Collie, Mary as a Poodle, Sybil as a Schipperke, Mr. Bates as a Basset Hound, and so on.
In other Downton news, the show's executive producer recently revealed major plot details from season three.
Somebody will be born, and somebody will die, somebody pretty key in the cast, unfortunately not going to make it. It's the 1920s now, Rebecca Eaton told The Orlando Sentinel earlier this month.
She also confirmed that Matthew and Mary do get married, after the near heart-stopping Christmas proposal in the season two finale.
Scroll down to watch Jimmy Fallon in Downton Sixbey.