Newly-released pictures show the former Coronation Street actress glammed up in 1920s attire for a sketch, which will air in less than two weeks.
It's currently unknown what character Michelle is playing, but she certainly seems to have adapted to her new role pretty well.
The 28-year-olds stuns in an embroidered coral dress, oozing retro glamour.
While Downton Abbey will come to an end for good on Christmas Day, fans of the show can enjoy a string of famous faces before the festive special.
Following in the footsteps of George Clooney, Michelle will also be joined in the sketch by Gordon Ramsay, Gok Wan, Jim Broadbent and Warwick Davis.
Catch the Downton Abbey sketch for Text Santa on 18 December at 8pm on ITV.
Try Reveal's digital edition on iPhone & iPad. Subscribe now & never miss an issue!