Michelle Dockery , the 31-year-old actress – who is best known for playing Lady Mary Crawley on 'Downton Abbey' – will lend her voice to an upcoming episode of the animated comedy.

According to Entertainment Weekly, Michelle will “appear in a cutaway gag on the Griffins’ television playing… an aristocrat in a British period drama”.

Celebrities who have recently appeared on 'Family Guy' include Jessica Biel, Drew Barrymore, Sofia Vergara, Ryan Reynolds, Johnny Depp, Elizabeth Banks and Kellan Lutz.

Meanwhile, creator Julian Fellowes recently revealed there will be "tough times" for Lady Mary in 'Downton Abbey's fourth series.

He insisted the new season will be a difficult one for Michelle's alter-ego following the death of husband Matthew Crawley in the Christmas special, explaining: "There are tough times for Lady Mary I think we can say that."

She is also still dealing with the death of her sister Lady Sybil and Michelle has spoken about her sadness when Jessica Brown Findlay's alter-ego was killed off, because the brunette beauty really misses her "distinctive" laugh. 

She said: "We knew a couple of weeks prior to filming the episode what was going happen to it felt like this huge build up. One of the last scenes we shot with Jessica was where the sisters say goodbye to her, and me and Laura Carmichael [Lady Edith] were just devastated playing it.

"We've spent three years of our lives together so Jessica going was as wrench. I miss her laugh, it's really distinctive."

Watch Downton Abbey: Michelle Dockery's Essential Mary Moments