I Once Found A Science Project Underneath The Seat Of My Car

Every time I go to clean out my car, I always find something that I didn't realize I lost or I don't have a clue how it got in there in the first place.  One time I found something that totally blew my mind.

A few summers ago I let my dad and brothers borrow my car for work.  When I got it back everything seemed to be in pretty good, clean condition.  It didn't smell the best but I attributed that to the fact that they had been working outside and it was hot.  I just put another air freshener in there and called it good.

One day it was really hot and I had the windows closed up.  I got in and it smelled pretty nasty.  I take that back, it was really nasty.  For the life of me I couldn't figure out what it was.  I tore my car apart trying to figure out the source of the smell and eventually I found it.  To this day I don't have a clue what exactly it was, I'm guessing a combination of things.

The smell was so bad I nearly gagged.  I'm assuming it didn't wreak before because I would leave windows cracked and it wasn't that hot.  Ugh, nasty!  Needless to say, I now check everywhere because I don't want any science projects in my vehicle.

What is the strangest thing you've found in your car that you didn't know was there?