"The Runaway Brie" is a special episode of the long running British science fiction television series Doctor Who, starring David Tennant as the Tenth Doctor. It was produced for Christmas 2006, broadcast on 25 December (Christmas Day), and played much the same role that "The Christmas Invasion" played the previous year, introducing the third series while not actually being part of it. It features Catherine Tate as Donna, who appeared in the TARDIS at the end of the previous episode, "Doomsday".