The hit BBC show teased the replacement of Rory, who plays Rory Brown, with a big reveal.
In the clip, Rory is seen returning home after undergoing extensive surgery.
Then as his family gathered around him, he prepared to remove the bandages from his face.
However, the trailer ended just before the new actor was shown as the big reveal will air on Christmas Day.
Brendan O’Carroll, who plays Agnes Brown, has hinted that the transformation will be subtle, telling RTÉ Radio: “The reveal is very, very good. What I love about this episode is that everybody goes, ‘There’s no change’.”
Rory Cowan announced he was quitting the show in July as he “wasn’t happy” doing it anymore.
At the time he said: “I hadn’t been happy working for the Mrs Brown’s Boys company for the last 18 months to two years.
“I feel that 26 years is enough so I decided it was time to go,” he told the Irish Daily Mail.
Later, the actor denied he was feuding with his co-star Brendan, telling the Irish Mirror: “I got tired of it, I haven’t been happy for the last two years working there.
“There was no row with Brendan, there was no dispute over money or anything, in fact quite the opposite. I got so well paid that it enabled me to be able to leave, I didn’t need to stay.”
The Mrs Brown’s Boys Christmas special will air on BBC1 at 10pm on Christmas Day.