We've designed these collapsible animal toys for 3D printing based on toys from our childhood that were made from wood. When you press the button that is spring-loaded, the strings that hold all the parts together get loosened and that makes the animal collapse. This model was made by Adrien from our 3Demon team.
We've made an instructables guide to show step by step how the toys are assembled, you can get access to it here : https://www.instructables.com/Collapsing-Animal-Toys/
We've also made a time-lapse of us assembling the fox which you can watch here: https://youtu.be/IPbs5YSo9A8