Warning: MUSIC THEORY AHEAD!
One of my favourite chords is the Neapolitan bii. To my ears, it's a very dramatic chord - it's quite a departure from the harmony you might expect, especially music from the 1700s.
As it turns out, the Neapolitan appears in invention #13. Funnily, I didn't hear it because it happens really fast. It wasn't until I was entering the notes into Pico-8 that I saw, then listened to Glenn Gould's version, THEN I heard it. It happens at the end of the piece, around 0:35.

It's really hard to hear in this piece... but it's there!