After rearranging the pressure washer pipes, I hauled the grill out on the driveway and opened the lid. My Shop Assistant denied putting that ball of fuzz in there:
Gingerly prying it open revealed a mouse-sized pocket in the middle:
And a bit of investigation uncovered the source of the batting. Evidently, the corner seam of the ancient lawn couch thing (which came with the house and has been unused for over a decade) sitting on the patio had burst, leaving just enough room for an industrious mouse:
They’d been camping inside the cushion at least over the winter and evidently used the far corner as their latrine. We bagged the whole cushion and added it to the van full of trash headed for the town’s bulk collection, which fortunately occurred that weekend.
Now, to haul the frame to the metal recycler and take advantage of the current commodity price bubble…