Strange Occurences...The Big Reveal

We have started cleaning house on Saturdays. I make a list of what needs to be done, and then everyone signs up for what they will do that day. It has worked well so far, but this weekend I have a lot of schoolwork to complete, so cleaning may not go well. Two weeks ago as we were cleaning, when #2 came outside to dispose of some maggotty acorns. He had put them in his chest and backpack in his bedroom. I used to have a student who would do the same thing in class in his pencil box. I had to make a classroom rule that there would be NO acorns brought into class. I have had to make that a house rule now. It was the same day that I found this in my refrigerator. Some of you have made good guesses, but all wrong. This mess was made by an egg that somehow got under the meat tray and broke. I understand why it broke, but how it got there is beyond me. #2 found some eggshell a few days before that on the bottom of the fridge, but I never thought it would mean there was an egg under the tray! So here I am with egg all over my refrigerator. Better than my face, I suppose.