Well, look who made a home here
 

My sister sent me this picture of a groundhog making a home in here engine cavity. They noticed it when their dog ran to the front of the Mazda and continued to bark. That thing didn't move when they hosed him, it to prodding with a stick! Luckily, unlike field mice, no damage to the wires.
https://cimg5.ibsrv.net/gimg/www.maz...d7cbae0d5d.jpg

Luckily, they didn't drive down the road with a stowaway.

Lucky it didn't get caught in the belts. Where I used to work, cats would get up in the engine on the lift trucks to stay warm. Talk about a mess when the guys didn't check their oil and open the engine cover.

I hear ya.
Many moons ago newly married and at my first job out of college I heard some faint meowing coming from my boss's car just after he drove in.
I told him and he had a bad look on his face and opened the hood.
We counted six kittens in various areas around the engine bay, he smiled and said, "holy crap, they're all there".
He lived 18 miles from where we worked.
His cat had her kittens in the barn and being larger and more explorative they somehow managed to get into the engine bay probably for the heat.
Needless to say, I brought one of them home to my wife that night.

When I was an LTO, we had a cold spell once that really got down there. (High was about -5 degrees F) We had a plant manager who was on an inspection tour of the plant and walked by as I was getting off break. I was talking to him about the weather as our propane powered lift trucks didn't like the cold so we would plug them in to keep the engines warm. He asked me why everybody was honking the horn when they got back on. I told him sometimes cats would crawl up inside and the horn would scare them out. Then I hit the horn. A kitten flew out from under the truck and mistook his leg for a tree. He was not a cat person to begin with and that didn't go over very well.