When I first saw this, I thought, hey cool! Then I took a screenshot and when it came through in the screenshot, that was even cooler. It's not often you get something like this. Memory corruption, maybe, not terminal, and not detected by the graphics software. My laptop gets hot sometimes, maybe the memory got corrupted that way? It happened on wake from sleep. Anyway, voila.

It sort of went away when it redrew areas of the screen but not completely, so I restarted.