So two years ago, I made an all grain pumpkin ale and let it ferment away. I got busy and ended up moving for two years and left the carboy at my friends house who I was renting a room from.
When I came back, the airlock had been broken and was filled with dried fruit flies. Luckily none of them got in.
There was a think beige film on the surface of the beer which I believe to be yeast. I think the layer of CO2 preserved the beer because I just syphoned off a gallon and its perfectly fine! It tastes a little old but not oxidized. I thought for sure it was malt vinegar by now
If you know what Baby Rain is, you win.