When my Zachi left me this morning, he appeared next to an egg. Does this mean that he left me an egg? And if so, will that egg become a really secret character or something?
I noticed my Sekitoritchi did the same thing before it passed away at 29. The Mothra tamagotchi also does this. When your guy dies at old age, from my understanding and using mothra logic, it means it layed an egg for you to carry on with in death. I don't think you get anything special out of it (it's how you raise it to determine that) but sounds like a final gesture of love like a thank you for just taking care of them so well. Since the p1's and p2's and the Mothra tama are not gender oriented (that's up to the owner) this thing seems to make sense to me.
Hope that made sense!