‘Downton Abbey’ Season 4 Spoilers: Paul Giamatti Joins Cast As Cora’s Brother, Harold Levinson [VIDEO]

Actor Paul Giamatti at the 2010 Toronto International Film Festival. Creative Commons

"Downton Abbey" is gaining another American actor for season 4! Paul Giamatti, best known for his role in "Sideways" and "Cinderealla Man" will be joining the cast of "Downton Abbey" as Harold Levinson. Harold is the playboy brother of Cora Crawley, and will serve as uncle to Cora's children, Mary and Edith.

Giamatti is set to first appear in the Season 4 finale, as he is currently filming Spider-Man 2 starring Andrew Garfield. Giamatti will premiere as Harold alongside returning guest star Shirley MacLaine, who plays Cora and Harold's mother, Martha.

Executive producer Gareth Neame revealed how thrilled he was to have the Emmy-award-winning actor join the cast, "we're excited that Paul Giamatti will be joining us on "Downton Abbey" to play Cora's brother Harold, the rather free-spirited uncle to Mary and Edith. We can't wait to see him work alongside Shirley MacLaine, who are both sure to upset the Grantham family's apple cart in this year's Christmas Day episode."

Giamatti is not the only new face in the cast of "Downton Abbey." Other new characters include Dame Harriet Walters, Nigel Harman, Tom Cullen and Gary Carr. Walters's character is an old friend of Dowager Violet Crawley, Harman will play a valet, and Cullen will serve as a new love interest for Mary Crawley, named Lord Anthony Gillingham, who helps the family with their financial issues.

As for Gary Carr, the "Death in Paradise" star will play the show's first black character. Carr will play a "charming and charismatic" Jazz singer named Jack Ross.

The season 3 finale was the highest-rated show on American television that evening with an average of 12.3milion viewers, the fourth season will premiere on PBS on Jan. 5, 2014.