The episode is to be titled 'Father Who?' and is to be a a twist on A Christmas Carol tweeted BBC entertainment correspondent Lizo Mzimba.
Showrunner Steve Moffat said on the Christmas episode:
"Michael Gambon is as distinguished an actor as I can imagine and the fact that he was Dumbledore means that he is already know to millions of children,"
"Oh, we're going for broke with this one. It's all your favourite Christmas movies at once, in an hour, with monsters. And The Doctor. And a honeymoon. And... oh, you'll see. I've honestly never been so excited about writing anything.
He added that he had not known that this was Katherine Jenkins's first major acting role before she was cast. "She is brilliant – she is a great singer and a great performer,".
BBC Press Release:
The adventure will star Matt Smith as the Doctor, alongside Karen Gillan as Amy and Arthur Darvill as Rory. They'll be joined by, amongst others, Michael Gambon, one of the industry's most respected actors who has starred in TV classics such as The Singing Detective and Longitude as well as Academy Award-winning films including Gosford Park and Sleepy Hollow. Recently he has become popular with a new generation, right across the world as Professor Albus Dumbledore in the Harry Potter movies.
Katherine Jenkins also stars in the special. She's currently best known as a mezzo-soprano and is one of the world's most successful classical singers. 'I'm over the moon to be involved in the Doctor Who Christmas Special!' Katherine said. 'I can't quite believe it as it's a part of the family tradition at the Jenkins household. I heard the news that I got the role on my 30th birthday and it was the best birthday present ever!'