The science of spinning eggs

This may look like a plastic egg standing on end but it is actually a spinning plastic egg. And, furthermore, it didn't start its spinning in its end. Messing about with some hollow plastic toy eggs with our toddler, I spun one on its side and, to my amazement, after a few turns, it stood up on end and spin on its tip. I repeated it many times during our little game and it always 'stood up' on one end or the other. Fresh eggs don't work (I tried. Carefully). They continue to spin on their sides. But we had blown some eggs for painting at Easter and they behave in the same way as the hollow plastic ones. I looked into the science of this, only to discover serious scientific studies in some of the most reputable journals explaining the phenomenon. Classically, the comparison is between boiled and fresh eggs. Boiled eggs stand up when on their side, fresh eggs don't. I didn't have boiled eggs to hand but I am happy to report that. Cadbury's cream egg can be spun like a boiled egg and will sometimes stand up! The explanation is to do with friction and unevenness in surfaces which directs some of the kinetic energy of a spinning egg upwards, enough to lift the centre of gravity and, for a time, cause the egg to spin standing upright. Fresh eggs have liquid inside and so (I think) the diverted kinetic energy is insufficient to overcome the inertia (?) of the moving liquid egg enough to cause the centre of gravity to lift. I think.