Call The Midwife star Cliff Parisi appeared on Good Morning Britain on Thursday where he chatted to hosts Alex Beresford and Charlotte Hawkins.
He was also joined by co-star Annabelle Apison, who plays Violet Buckle in the BBC show, which will air a 90-minute Christmas special on Christmas Day.
Cliff, who plays Fred Buckle, teased: "This year we have got a circus coming to town, I am obviously up to my usual tricks with a get rich quick scheme that goes a bit wrong.
"Trixie gets the hump because someone signs her up to a subscription for a marriage bureau.
"And Sister Monica Joan gets rushed into hospital on Christmas Day.
"And we have got Peter Davidson who is the ringmaster for the circus."
Annabelle interjected: "And very important, Father Christmas gets stuck coming down the chimney and they have to call the fire brigade!"
The Christmas special for the show was all shot during lockdown amid the pandemic, with social distancing on set.
Cliff revealed the actors wore masks right up until the moment the camera started rolling.
"It was a bit strange, but our producer put all the PPE in place, made them very simple for us, all e had to do was remember to take our masks off before they say, 'Action!'"
Paying tribute to his former EastEnders star Barbara Windsor, Cliff said she was like a social workers as she would always sort everyone's problems behind the camera.
He said: "She was an incredible woman, she could do it all and she had done it all.
"She was very good at reading problems and sorting them out, she was the go to person if something was wrong.
"And if you were naughty she shouted at you, she shouted at me a few times!"
Call the Midwife Christmas special airs at 7:40pm on 25th December on BBC One
