Ask HN: A pixel on my screen is walking like a bug. What could it be?

Yesterday morning I began noticing what I first assumed was a very small insect meandering around on my screen. I quickly realized that it was not an insect after I tried to squish it (the dot just kept moving about).

I then realized it was a single pixel, or a dot the size of a pixel, that moves around my screen in a meandering fashion, very similar to how an insect moves. It tends to focus around the top left of the screen, but "meanders" all the way to the right sometimes as if it's looking for something.

My next thought was malware. I attempted a screen recording using Quicktime but was surprised to find that the meandering pixel did not show up in a screen recording. Hmm.

I was able to record it on my phone.

Any ideas what this could be?