I placed some excess porridge (oats) I had cooked in a tightly sealing Tupper container, and placed it on top of the 'fridge. It was intended to be eaten later that day. Unfortunately, it was somehow knocked down the back of the 'fridge and jammed in the cooling fins.
It wasn't until I knocked something else off the top of the refrigerator that I noticed the porridge container. This must have been, at least, two months later.
It was with some trepidation that I opened the container as I was expecting a foul smell. What I discovered was a smell worse than anything you could possibly imagine. The sealed container, warm conditions and particularly the long period of storage contributed to making the worst kind of fermentation imaginable. Completely cleaning the container and then a long steep in a strong bleach solution still hasn't removed the smell. "Nuke it from orbit" might be the only way to deal with this Tupper container.