Changed the default login from Xorg (which works for everyone) to Wayland (which doesn't work for most things GNOMISH), and forgot to mention it to anyone. Created all sorts of display, theming, and application problems. Basically, a dev had it switched to Wayland when it was published and nobody noticed it until then. It was not mentioned in the Arch Testing forum, either. Kind of a cruel joke, but the fix was easy--change login back to Xorg. It's just nobody was expecting it--until it happened to them.
It reminded me of an old Folger's Crystals commercial. The one where they switch out the really good coffee for the crap crystals, and see if the unknowing coffee drinker notices.
Only this wasn't quite as cute--except maybe if you were running Plasma. Muahaha--take that, you buncha garden statue-loving people!