37. Donna Noble Enters the Doctor's Life
From: "The Runaway Bride"
Premiere: December 25, 2008
Casting British comedian Catherine Tate as Donna Noble, Tenth Doctor David Tennant's third and final companion, was a risky gamble that paid off handsomely. Making her debut as a principal extra in a Christmas episode, Tate was a brassy balance to the cerebral Doctor, the likes of which had only been hinted at by previous companions like mouthy Australian stewardess Tegan Jovanka (Janet Fielding) and perky computer programmer Melanie Bush (Bonnie Langford).