Vital Science on the Resonant Frequency of Googly Eyes
All objects have a resonant frequency, the natural frequency (or frequencies) that makes them vibrate. That's why a really, really good opera singer could theoretically shatter a wineglass with a particularly high note. They'd just have to hit the resonant frequency.
Even googly eyes have a resonant frequency. One intrepid experimenter found it, making a collection of googly eyes go even more googly-eyed than normal, vibrating back and forth in a sort of plastic rapture.
That frequency happens to be 433 Hz. Useful to know in case you ever want to make your craft project go cross-eyed.