This model has pleasing action as it morphs when you push on the sides. If you do an internet search on “fidget worm” you will see commercial versions.

The OpenSCAD source file is included. You can make your own variations. The scad program creates a large articulate matrix from which you can cut out the shape you want. In my program, a scaled sphere is cut out of the matrix.

Printing requires support. After printing and removing the support material, it's quite pleasing to push on it to get the first fold. Then the folding gets even easier as you fidget with it. I prefer to sand the outside surface to remove any pokey pits of plastic. For very smooth action, spray the entire model with a lubricant, then wipe off the excess.

Update, I made 3 more versions here: 

https://www.printables.com/model/885626-folding-fidget-v2-scad