There are some cat toys at the house that are particularly popular with the local residents. They are simple hollow spheres with cut-out slots. They are great for kitties to kick around — small and light. After staring at one for a few minutes, piecing out the geometry, I realized that this would make a great instructional design for an introduction to 3D CAD modeling using simple geometric shapes and boolean transforms.

In the main image are the original (left), render (middle), and printed (right) versions of this object.

The step-by-step process of building the model is on my blog, here: http://netninja.com/2012/03/24/from-atoms-to-bits-to-atoms-a-cat-toys-journey/

The final fully parametric OpenSCAD file is attached.