When my DD was 3, we went to her grandparents house. As we pulled up in the car, DD said, where are the lights?
The last time she was there was at xmas time, when she was 6 months old!!!
My inlaws thought we must have had pictures of the outside of the house that we had showed DD, but we did not.
Edited to add:
DD doesn't do this sort of thing anymore, however. Now she's 6 1/2, and can't remember what happened last week!