Donna Noble
Bernard Cribbins, who appeared in the story "Voyage of the Damned" and throughout Series 4 as Wilfred Mott, grandfather of Donna Noble, acts as the companion to the Doctor in this two-part story. The special also features the return of many other actors to the show, including Catherine Tate, John Simm, Jacqueline King, Alexandra Moen, Billie Piper, Camille Coduri, Freema Agyeman, Noel Clarke, John Barrowman, Elisabeth Sladen, Tommy Knight, Jessica Hynes and Russell Tovey.