Like others, I thought from the title of this thread, we were going to get some really weird "look what we found in the office fridge!" stories. I've come across TOO MANY in my working career.
There is one story that everyone in our office of 40 know about. I work at an investment bank and there was an analyst who had just come back from a trip in India. He had been having troubles for about 2 weeks so during work, he took a break to go see the doctor. A couple days went by after he had seen the doctor, when an admin assistant looking for left overs found a small odd bottle inside the fridge. Upon inspection, she realized it was actually "biohazard!"
Turns out the guy's doctor had asked for a sample of his stool. He took a sample, and thought he'd keep it "fresh" by putting it in the fridge. No one knew how long it had been sitting there, but obviously some people have no idea what normal hygiene habits are - which was no surprise when he started getting stomach troubles in the first place.