See Photos of the "Downton Abbey" Cast Then and Now

Prior to being cast as Robert, the Earl of Grantham, Bonneville worked steadily in British TV and movies. He was probably best known for his comic characters, like his role as Bernie in "Notting Hill."

McGovern came into her role as Cora, the Countess of Grantham, with some serious honours under her belt already. In 1981, she earned her first Oscar nomination for best supporting actress for her role in "Ragtime." She also starred in several other high-profile movies, and in 2007, she formed a band, Sadie and the Hotheads.

It's impossible to imagine anyone else playing Violet Crawley, the Dowager Countess of Grantham, other than living legend Maggie Smith. When she debuted "Downton" in 2010, she had already won two Oscars, a Tony Award, and four Emmys, along with a slew of other accolades, including the title of "Dame" bestowed by Queen Elizabeth II.

Before being cast as Lady Mary Crawley, the eldest of the three Crawley sisters, Dockery was just launching her career with a handful of British TV dramas, mostly classical adaptations. She actually shared the screen with her future "Downton" leading man, Dan Stevens, in a 2009 adaptation of "The Turn of the Screw."

As perpetually-overlooked second daughter Lady Edith Crawley, Carmichael took on the tough task of getting audiences to root for such a complicated character. "Downton" marked Carmichael's first major acting gig.

Leech made a splash as Tom Branson, the charming and rebellious Irish socialist who takes a job as the Crawleys' chaffeur, only to find a friend (and then some) in progressive-minded Lady Sybil. He was already a rising star in the Irish film industry, with acclaimed roles in projects like "Cowboys and Angels" and "Love Is the Drug." American audiences might have also recognised him from his role as Marcus Agrippa on the TV series "Rome."

Like many of his "Downton" costars, Coyle had a solid career in British film and TV before taking on the role of taciturn valet John Bates. His resume included dozens of TV movies and series, including beloved adaptations like "North and South" and "Lark Rise to Candleford."

Coyle has continued a similar career trajectory since hitting it big with "Downton." He has appeared in major movies like "Me Before You" and "Mary Queen of Scots," as well as several TV shows, including a main role in "Requiem."

Before being cast as loyal, big-hearted maid Anna on "Downton," Froggatt's early career consisted largely of British soap operas and TV movies. Her credits included the long-running "Coronation Street," the BBC retelling of "Robin Hood," a handful of true-crime TV movies, and several BBC radio plays.

Froggatt continues to work steadily, from movies and TV to stage and radio. Her projects have been a little bit smaller in scale, from thrillers like "Liar" and "Angela Black" to voice work on "Bob the Builder."

Long before he was the Crawleys' loyal (if uptight) butler Carson, Carter had carved out a decades-long and highly respected career in film and TV. He was part of the quirky ensemble in "Shakespeare in Love," appeared in family movies like "Ella Enchanted" and "The Golden Compass," and earned acclaim for dramas like "Cranford."

No-nonsense but good-hearted housekeeper Mrs. Hughes is one of the people who keeps Downton running. Prior to taking on the role of Mrs. Hughes, Logan lengthy career was probably best known, through her lengthy career, for her role as Lady Jane Felsham on the British dramedy "Lovejoy."

Logan has had a slew of new TV shows and movies since "Downton." Along with several guest and supporting roles, she's starred in British TV shows like "Girlfriends" and movies like "The Last Bus."

As scheming footman Thomas, James-Collier has taken his "Downton" role all the way from villain to hero. Playing Thomas was his major breakout; prior to that, his most notable credit was an arc on the British soap "Coronation Street."