I was working in a customers house a few years ago; when I neighbor knocked at the door, and informed me my lights were on in my truck.
We both walked outside, and sure enough, they were on.
As I got closer I notice a squirrel running around inside the truck!
I opened both doors to let him out; he took off like a rocket.
On closer inspection, I saw that he had gotten into my lunch, and also tore into my new seat covers; while defecating all over, inside.
He gained entrance through the sunroof, It was tilted up about 2".
As for the headlights being on; It seems he hit the paddle switch while doing laps around the inside of the truck.
The neighbor mentioned later that they have many squirrel problems in that neighborhood.