Doctor Who: 5 NuWho Episodes That Were Actually Sequels Or Prequels To Classic Stories
2. The Snowmen
In 'The Snowmen', the first of Series 7's two Christmas Specials, The Eleventh Doctor faces The Great Intelligence for the first time since The Second Doctor story, 'The Web Of Fear'.
In one of a few confrontations between The Doctor and The Intelligence during the special, The Doctor declares that the London Underground 'is a key strategic weakness of Metropolitan living'. The Great Intelligence claims not to know what The Doctor is talking about.
It has been suggested that The Doctor inadvertently gave The Great Intelligence the idea to attack the London Underground. This would make 'The Snowmen' a prequel to the classic serial 'The Abominable Snowmen', a Second Doctor story featuring the first appearance of The Great Intelligence. In that story, the Intelligence uses robot Yetis in an attack on the London Underground.