The shaking represents any sort of action that doesn't perform a measurement. It was the first thing I thought of that could affect the ball without opening the

The shaking represents any sort of action that doesn't perform a measurement. It was the first thing I thought of that could affect the ball without opening the box. It could be that the shaking didn't have an effect. But equally, it could have had an effect. The spooky bit is that the other ball 'knows' whether it did or not in a non-local way.