Summary

It is an Easter egg version of the sliding Christmas tree. The two parts slide into each other but not through each other. An OpenSCAD model is attached, which you can use to customize the egg. After exporting, be sure to rotate (not mirror!) the parts so that they sit on their filled ends on the build plate. Minimal detachable support is enough, as seen in the attached photo. If you reduce the gap, the parts will stick.

Base egg scad credits: https://github.com/DrT0M/egg.scad