Doctor Who: 17 Cool Details Steven Moffat Just Revealed About The Eleventh Hour

While little Amelia is packing her suitcase, the camera pans past one of the doors on her landing, which has mysteriously opened all by itself.

Then, when the episode cuts back to adult Amy, this door is brought up again, with the Doctor asking her to count how many rooms she can see. Even though she's lived here since she was a child, Amy fails to count that mysterious door, prompting the Doctor to reveal that she missed it because it was being masked by a perception filter.

This idea of an old house hiding a secret room stemmed from Moffat's childhood, and more specifically, a dream he used to have about his grandma's house.

The writer tweeted that he had a recurring dream about an extra door on the landing of his grandma's house, which led to a strange green room full of toys and tables. Every time he went to visit his grandma in reality, he would run upstairs to check if the door was there, but it never was.

A strange night terror to experience, sure, but it came in handy eventually!