A few days ago I made some cornbread. The recipe involved soaking polenta in buttermilk overnight and then adding the rest of the ingredients (flour, sugar, baking soda, baking powder, corn, eggs, butter, etc.). It didn't come out very well, but I hate to throw things out unless they're really bad (this was only sort of bad), so I left it on the counter with the pan covered in foil.
Last night I decided to give up on the cornbread and toss it. I lifted up the top piece of foil and noticed that there were black specks on it and the other piece. Then I looked closer and realized that what I thought was black specks was holes in the foil! Where the foil touched the cornbread, it had eaten holes through both layers. There were gray specks on the top of the cornbread. What could have caused this? I've never seen anything like it... The good part of this was that I felt completely justified in throwing out the cornbread! :]