A largely forgettable story that really didn't need to be a two-parter; only exists to explain why Amy Pond has been cloned, and raises some ethical issues that aren't really all that gripping.
79. Aliens Of London/World War Three
Great set-up undercut by farting aliens. Seriously Russell T Davies, you're going to juxtapose the image a spaceship tearing through Big Ben with green teletubbies?
78. Voyage Of The Damned
The Doctor meets Kylie Minogue on a spaceship named after the Titanic, and the reveal of Max Capricorn is nearly as huge a disappointment as the fact he was beaten with a forklift.
77. Cold War
Completely mirroring 'Dalek', 'Cold War' centres on an Ice Warrior loose on a submarine in the 80's. Except more Ice Warriors inexplicably turn up out of nowhere at the end to save both sides; meanwhile, the TARDIS randomly disappears.
76. Fear Her
The Doctor's exceptionally alien and the concept's great, but there's no escaping Ten and Rose's smugness, or the fact the production team can't create a real-looking Olympic Games.