Our furnace is getting on in years, well over 20 years old. It has been acting up a lot and we had to have the service guy come out twice in the same week. The first time it was the filter plug, but the second time there was a lot of drilling and banging and finally he came up to ask me to come down and see something.
He found these in our intake pipe. How funny! From the condition of the eggs, and the contents inside, these eggs were not from this year. Chances are, these were hidden last year in the intake pipe on the side of our house. When the furnace came on, it sucked them into the pipe and eventually they got stuck, causing our furnace to act up. Most likely it was an adult that hid them there, since this year was the first year that the teens hid the eggs for the little ones.