Invasion of the squirrel kind.

I came in to the lab to find a visitor there... building a nest.

Video evidence right here.

Some one left the window open overnight and this little one started building a nest here. Harvesting materials from the vines and from the paper towels in the room. We had to close the window after this. Better now so the squirrel could get start on a new nest faster rather than later with the far less nice exterminator.

Some image evidence of the rascal too from the time we were thinking "Aww, she's getting things for her nest in the vines".. not in the next room: