The actress will make her debut as Clara's grandmother, while James Buller returns as Clara's father following his appearance in 'The Rings of Akhaten' earlier this year.
Doctor Who: Daleks, Cybermen in Matt Smith finale - pictures
According to the Radio Times, Elizabeth Rider will star as Linda, Only Fools and Horses actress Tessa Peake-Jones will play Marta and Facejacker's Kayvan Novak will voice Handles.
Meanwhile, Mark Anthony Brighton will play Colonel Albero, Sonita Henry will be Colonel Meme, Rob Jarvis will play Abramel and Jack Hollington will appear as Barnable.
The festive episode marks the last appearance of Matt Smith as The Doctor, while Peter Capaldi will make his first full appearance in the role.
'The Time of the Doctor' airs on Christmas Day at 7.30pm on BBC One.