What Is That Instrument in Upa and Bora's Theme?

[Gaffer Tape]

So the piece of music used as Upa and Bora's theme is one of my new favorites in the series. For those of you unfamiliar, this is it:

https://www.youtube.com/watch?v=u7hNftKJcJs

I know a lot of people who rail on Kikuchi's score make the claim that his use of the "rattling sound" (which is actually a vibroslap) and the "boingy sound" diminish the drama on serious tracks. I've always personally disagreed with such claims, feeling that those instruments are well-integrated into the arrangement so that they don't really stand out but rather contribute to the whole. However, this is what I find to be the one exception, and I feel the boingy sound is really overused here, to the point that it detracts from the melody. Anyway, my question is, what instrument is that anyway, because I sound remarkably stupid calling it "the boingy sound"?

[kenisu3000]

It's called a Jew's harp.

I recently watched A Boy Named Charlie Brown, and Snoopy has this running gag/schtick throughout the movie where he pulls one out and plays it.

[Gaffer Tape]

Oh, my gosh! Obviously! How did I not figure that out? How did I not make that connection? Thanks, kenisu3000