Doomsday (The Girl Who Loved Doctor Who)

In a parallel universe, Doomsday was an episode of the television series Doctor Who.

The episode depicted a fictional version of the Battle of Canary Wharf that took place in the Doctor's universe. When a Cyberman from the actual battle slipped into this parallel universe after the fact, Ally recognised the Cyberman as being from the episode. (COMIC: The Girl Who Loved Doctor Who)