The video was released just one day after the first photos were published of George posing with Hugh Bonneville, who stars in the hit show as Robert Crawley, The Earl of Grantham.
The very brief teaser sees Lady Cora, played by Elizabeth McGovern, discussing a dinner invitation to the back of someone viewers are led to believe is Hugh's character.
As the Christmas song, “Let It Snow,” plays in the background, the man turns around, revealing himself to be none other than George, looking dapper in a three-piece suit.
The full sketch is due to be aired on Dec. 18, as part of the UK network’s Text Santa campaign.
George joined the Downton cast for filming at Highclere Castle earlier this year. Details of the plot have been shrouded in secrecy - although Laura Carmichael has revealed there’s an amusing scene between George and Dame Maggie Smith, who stars as the Dowager Countess of Grantham.
“There’s a very brilliant moment with Maggie and George – I don’t know if I want to give away any more than that really – but George wants a kiss, and Maggie end up on the floor. It’s wonderful,” the actress, who plays Lady Edith, told ITV’s This Morning.
George Clooney with Downton’s Hugh Bonneville
Hugh, who co-starred with George in the 2014 film The Monuments Men, recently spoke about the Hollywood star’s visit to the set.
“He came and filmed with us for an afternoon back in May when we were doing this Text Santa sketch and he was incredibly generous with his time and his talent,” Hugh said.
“It’s interesting the number of people who suddenly came on set who’d never been on set in five years of filming,” he added. “He was great – he was a good laugh and sprinkled some sort of magic dust over our experience.”