8. New Earth
Most new Doctors feature familiar characters and enemies to help ease in the transition. The Eleventh Doctor faced the Daleks early in his run, and the Twelfth Doctor adventured with the Paternoster Gang. New Earth saw the return of Cassandra and the Face of Boe. Yes, Cassandra is the very epitome of camp, and a character many would like to forget. But she was very memorable. The Michael Jackson-esque character featured in two parts of this loose trilogy and her nefarious ploys gave way to a vulnerable past. This was a prime example of Doctor Who doing sincere, and it worked exceptionally well. But prior to all this the viewers saw a zombie-like plague sweep through the New New York Hospital and some feminine acting from Tennant. Like Love & Monsters this episode divided public opinion, but it did greet the viewers with their first glimpse of an alien world (albeit, one which looked pretty much identical to our own) and it sparked the romance between the Doctor and Rose. And it was all down to Cassandras meddling. Surely you all have to be thankful for that at least.