Ok, perhaps not so much sound-related (though there is some music playing in the background), but it's rather sciencey.
I'd just glued some labels onto some string-tie envelopes we use for packaging and then put them back into the plastic "boxes" that we receive the envelopes in. I later noticed something moving around inside and for a moment thought some sort of bug had got inside. It turned out to be just a little round piece of kraft paper which had come out of one of the rivet holes used for the string tie discs. It eventually settled down, but when I rubbed my finger over the plastic box, it went into its little dance again. So I grabbed my iPad and shot a little video of it.