Anyone who has raised chickens for a while has certainly seen some strange eggs laid by the hens. I have seen a small egg inside of a large egg, double yolk eggs, long thin shaped eggs, and probably others that I can’t think of at the moment. The most common “strange egg” that I have seen is the “egg with no shell”. These literally have no shell, but they do have the tough leathery skin that lines the inside of a normal egg shell. They have a pale translucent appearance. They begin to shrink fairly quickly as the water evaporates through that leathery skin. Since it is the inside that is shrinking while the outer skin remains the same size, it soon loses it’s round egg shape.
Keep in mind that this same evaporation and shrinking also occurs in regular eggs since the shell is porous. That is why you can approximate the age of an egg by seeing if it floats or sinks in a glass of water. As the egg ages, it loses water and air is pulled in through the shell to displace the lost water. That is the air sac that is at the end of an egg. The older the egg is, the more water is lost; air is pulled into the egg causing it to float rather than sink.