I designed this so that it could attach to wooden face I laser cut. The servo would be stuck to a rectangular face which acts as base and the servo would be attached to a face above it which would rotate. The measurements were hard to be precise with so the fitting is a bit lose. The following video demonstrates it.

However, I decided to experiment with the mechanism by removing the top face and just letting one face stay. What I found was simple yet amusing, and the first thought that came into my mind was that any child seeing this would appreciate it. I present you the dancing face (switch on sound for a fun rhythm):

The code I was used were simple repititions where I tried to vary the time to create the rhythm in the video.

#include <Servo.h>
Servo hi;

void setup()
{
  hi.attach(9);
}

void loop()
{
  hi.write(0);
  delay(1000);

  hi.write(180);
  delay(1000);

  hi.write(0);
  delay(100);

  hi.write(180);
  delay(100);
  
  hi.write(0);
  delay(500);

  hi.write(180);
  delay(500);
  
  hi.write(0);
  delay(1000);

  hi.write(180);
  delay(1000);

  for (int i=1;i<10;i++){
  hi.write(0);
  delay(100);
  hi.write(180);
  delay(100);
  }

  for (int i=1;i<5;i++){
  hi.write(0);
  delay(500);
  hi.write(180);
  delay(500);
  }

   hi.write(0);
  delay(1000);

  hi.write(180);
  delay(1000);

  hi.write(0);
  delay(100);

  hi.write(180);
  delay(100);
  
  hi.write(0);
  delay(500);

  hi.write(180);
  delay(500);
  
  hi.write(0);
  delay(1000);

  hi.write(180);
  delay(1000);
}