8. The Deadly Assassin (Fourth Doctor)
This peculiar story starts off being rather confusing, but quickly it all begins to make sense. The story begins where the former serial (Hand of Fear) ended. The Doctor has received a call from Gallifrey declaring he must return. Alone. He must sadly take Sarah Jane home, then whisks off to his home planet, and thus The Deadly Assassin begins. Almost immediately upon arriving, the Doctor witnesses the Lord President being assassinated. Soon it's shown that all this was merely a hallucination, and when he does in fact arrive at Gallifrey, his TARDIS is impounded and the guards are ordered to arrest the occupant. The Doctor realizes that the Time Lords were not responsible for his summoning, and also learns that his hallucination about the Lord President's assassination is about to come true. (This story is also notable for being the only one of the classic series to feature no companions)
7. The Empty Child/The Doctor Dances (Ninth Doctor)
"Moooommmmyyyyyy...." If you've seen this two-parter from 2005, that line thoroughly freaks you out. If you have not seen this, allow me to explain.... The ninth Doctor and Rose Tyler land in London during the Blitz, where they encounter a strange child wearing a gas mask (pictured above) who wanders around calling out for his mother. Before they can approach the child, a young girl warns them to stay away from him. They learn that he actually carries a disease that will infect anyone he touches, and when you get infected, you become exactly like him. Gas mask and all. They set out to discover the cause and cure, and also meet a con man named Jack Harkness who would go on to appear in many more episodes, and even his
own spin-off show.