Not me, but my parents, though I discovered it during a visit.
Bats. They had a bat infestation. This was up at the highest point of the house in the loft, they were remodeling and left the walls open - a hole to the outside let one in, and I guess a bunch decided it was a nice place to hang out. There were dozens.
As for dealing with it - bats are endangered, so you can't exterminate them. If I remember correctly the total spend was just over 10 grand. This also included installing multiple permanent one way doors so if any bats manage to get in again, they have multiple ways to get out.
This is exactly why I do the dishes after a good meal. I can't relax with the thought of a sink full of dishes, they need to be handled!