The “Twitchy Cat” Halloween prop is my take on the “Undead Kitty” by Oak Lane Cemetery.  This part replaces a brass rod, making the assembly much simpler and the mechanism more reliable.  So this is of interest only to those trying to replicate Twitchy Cat.

You can learn more about Twitchy Cat on Github:  https://github.com/aidtopia/twitchy_cat

In the photos, the green piece is the link.  It connects the actuator to the spine of the cat skeleton.  The hole takes a #6 x 1/2" screw which runs through the nose of the actuator and is held in place by a hex nut in the recess on the opposite side.  The other end of the link has a channel for a cable tie to hold it flat against the spine of the cat skeleton.  The “wing” on the side of the link is an anchor point for the return spring.

If you have only metric hardware, you can modify the OpenSCAD source.  An M3.5 or M4 is probably the best choice.

Print in the material of your choice.  I used PETG, but it seems PLA is sufficiently strong as well.  I recommend 0.2 mm layer height with default Prusa Slicer settings.  No supports needed.