Here is a "toy within a toy" that's inspired by a couple of things - totem poles, Russian dolls and children's building blocks. The design comes in six parts, three large ones and three small ones, each depicting a different animal. Parts of the same size can be stacked together, or you can treat them separately and have fun with some role-playing. :)
In addition, the smaller parts can be hidden inside the larger ones, just like a Russian doll concept (or perhaps a game of hide-and-seek!).
When I designed this toy, I was hoping that I could make something that's fun and entertaining to young kids. It is not really the classic surprise egg, but I think the surprise comes in finding a toy within a toy. In addition, a couple of things can be learnt by them since each of the animals live in different habitats.
Update: I have separated each of the pieces so you can now print them in different colours :)
This object was made in Tinkercad. https://www.tinkercad.com/things/fDD1Uzo5Cdx