About 20 years ago, I was renovating an old cottage that had been infested with mice and squirrels. I gutted the entire place down to the studs and rebuilt everything. While I was at it, I removed all the wiring to the build and redid it all too. As I worked around the main electrical panel, the panel was separated in two partitions. The first partition was where all the house wiring went to ... the other side was for servicing by the electrical company to install or reinstall or service the panel ... I never needed to go in there. So I worked on the place for about a month until I had to get behind the panel to remove a few screws. and adjust a few things.
I opened the never opened panel ...... I couldn't see any wires ..... the whole section of that panel was completely blocked by a recently deceased squirrel that was completely spread out, all limbs stretching as far as they could go in four directions and its tail completely ballooned up with fur. I took the out the squirrel as one solid stiff piece. It had entered in through a punch out that shouldn't have been removed and crawled in and touched things it shouldn't have touched.
I just didn't expect to find that when I went to open the metal box panel.
I wish I had taken a picture but it was just before the period when people started to get camera phones to take pictures of everything.