We were spending the day hanging out in our apartment. The light outside was gray and overcast. Throughout the day, I noticed snakes outside. Generally very large ones. Mostly, they were being carried across the street by somewhat furtive, shady-looking men (or maybe it was the same man each time?) to our side of the street.
Then, looking out the window to the apartment building on the other side of the street, I saw what I first took to be the source of all these snakes. A giant--I mean, two or three feet thick--boa constrictor seemed to be writhing behind the windows of the apartment opposite ours.
Then I realized my perception of depth was completely wrong. It wasn't a giant snake across the street; it was a merely large snake just outside our own window. It was sort of hanging from the concrete ledge above our window, but probing downwards, looking for a place to climb onto, and very much in danger of falling.
We opened the window to let it in, and it immediately took a shit on our windowsill the instant it was past the threshold.