The following images and video show a proof of concept on how two parts can be held together. One version is based on a clamp design, and the other uses a short piece of 1.75 mm filament with molten tips as a rivet joint.
This design is inspired by the STEMFIE motor enclosure designed by Brendon Collecutt.
This toy is unsuitable for children under three years due to choking hazards! 
