For the curious and persistent cat.

Very easy print with 2 options to print (* see also update):

Print-in-place version with the ball. Shake the ball loose after printing (or pause just before printing from the bottom of the treat compartment and break it loose).
Version without a ball: Add a small steel ball or small marble just before printing the bottom of the treat compartment (use pause).
Use support on the bed only for printing and 100% infill for proper weight distribution. Sand the supported area for smooth operation.

Just put one or a few treats in the egg (don't fill them all the way) so as not to make them top heavy.

The wall thickness has been chosen to be durable so that it can be beaten hard through the room (by the cat of course!). The size such that it will not be bitten quickly. That way it is also safe for the cat itself.

Update:

After testing, I wanted to let the egg have a more upright position in rest. It turned out that some extra weight was needed at the bottom of the egg. Side effect is that it makes it a bit more difficult to take out the treats for the cat.

For that I added version 2a & 2b. In the bottom part of the egg is a recess for a nut M8 or 5/16" (hexagon 13.2mm - height 7mm). It is now also possible that the egg comes to rest perfectly upright because the bottom is flattened.

With version 2a, the intention is to add a pause after printing 8mm to apply the nut and then continue printing. The nut is then completely invisible embedded in the egg. In version 2b, the hexagonal recess has been extended to the bottom so that the nut can be applied afterwards by means of gluing. (the nut will be visible). For both versions, the internal ball is also present. It is not necessary to apply a steel ball or marble.

For both versions 2a & 2b also Use support on the bed only for printing and 100% infill for proper weight distribution..

“How do I get that treat out?”“Wait, if I hit it?” “Nope... not that easy..”“Why doesn't that egg just stay there and wobble all the time?”“Wait... I just need to hit harder...”“Yes!”Let's repeat that......“There must be more in it, after all I hear it... This is fun!”