Summary

It's planet gears in a key hanger with a cat theme.
It's cute and fun to play with. It's also hard to print it.

It was inspired by my cat, and the screwless cube gears that people always like to play with. And someone totaly energic about the cube gears print.
I wanted something that people could still play with and be inspired by, but that would also fit in your pocket.

Instructions

First print the knob upside down.
Then print 3 small gears.
Check if they fit.
Next, you need to slice the center gear (upside down again), and modify the GCode so you have the printer head move away half way during the print, and then add the knob on the gear during the print.
Finally slice the case, and also have a pause in here to insert the 3 small gears and the knob+center gear.

Note: It took me quite a few test prints to get this to print correctly, fit and work. Took me a full day to design and print correctly. You also need to be able to print proper bridges at thin layers.

Finally give it away, and make someone happy. Because you should always give prints away IMHO.

Notes:

Printed at 0.1mm layers.
The broken gear was not because the gears are figile, but because that gear was slightly to large, and thus broke when trying to fit it.
My branch of Marlin has a M0/M1 stop command if you have an LCD panel. This really helps in inserting the previous prints.

Cat gears key chain.