'Downton Abbey' Season 4 Finale: Paul Giamatti, Shirley MacLaine On Set (PHOTO)

The Levinsons are coming to "Downton Abbey" for the Season 4 finale.

Paul Giamatti will make his first appearance as Harold Levinson, Cora's (Elizabeth McGovern) brother and Shirley MacLaine will return as their mother, Martha. The American actors were snapped on set filming a scene together.

downton abbey giamatti

"We're excited that Paul Giamatti will be joining us on 'Downton' to play Cora's brother Harold, the rather free-spirited uncle to Mary and Edith," Gareth Neame, managing director of Carnival Films, said in a statement. "We can't wait to see him work alongside Shirley MacLaine, who are both sure to upset the Grantham's apple cart in this year's finale.”

Giamatti is just one of the many new faces on "Downton Abbey" for Season 4. Daisy Lewis will play Sybil's new nanny, Gary Carr will play jazz singer Jack Ross and Tom Cullen, Nigel Harman, Dame Harriet Walter, Joanna David, Julian Ovenden and Dame Kiri Te Kanawa will also appear in "Downton Abbey."

Click through the slideshow below to see new Season 4 photos.

"Downton Abbey" premieres Sunday, January 5, 2014 on PBS.

"Downton Abbey"