For the curious and persistent cat. (Ferrets would love it too!)

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

• Print-in-place version with the ball. Shake the ball loose after printing, you may have to hit a bit harder on a hard surface like a table (or pause just before printing from the bottom of the treat compartment and break it loose).
• Version without a ball (for less or no noise): Add a small steel ball or small marble just before printing the bottom of the treat compartment (use pause), or don't put anything in it.

Use support on the bed only for printing and 100% infill to ensure enough weight is created.

Just put one or two 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.

Video is version 2a with added M8 Nut.
Printed with nozzle 0.4, layer thickness 0.2 and support on buildplate only!
Yellow, color change at 8mm (where the nut is), Emerald Green, color change at 40.8mm (part with bal) and Lava Red (part for the treats).
Used fuzzy mode outside walls (fuzzy skin point distance 0.3 and fuzzy skin thickness 0.2)

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 get the treats out 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" (recess is hexagon 13.2mm - height 7mm) or anything else that can act as weight e.g. washers. Now the egg comes mostly to rest perfectly upright because the bottom is slightly 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 squeezing in and 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 100% infill!

“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!”