While working on The Demo, I was obsessed with creating realistic looking television static. This sounds much easier than it sounds, since "random number" generators are only pseudorandom, and while this works fine normally, when rendering pixels for a 320x240 screen, you end up noticing patterns.
The first few attempts ended up with a flashing shimmering mess. After a while of experimentation, I came up with a way to render the pixels that didn't appear to have patterns in it. I was quite happy with the result.
I eventually re-integrated the results back into The Demo.