CW: Photosensitivity Hazard
Animated GIF
Context: I’ve been working on having the contents of the banks be “fully relocatable”, which entails making sure all the pointer constants in the code/data use labels instead of hardcoded numbers. Reaching this milestone for each bank is important because it will allow hackers to add code/data to banks without worrying about breaking things.
I’ve been doing informal tests here by just putting an extra nop at the beginning of the bank and seeing if anything breaks. Apparently, in this case, I didn’t have labels for (a) the pointer table for enemy sprites or (b) the palette table for the fade-in effect, which resulted in that lovely, terrifying mess. (I’m surprised the game didn’t crash, honestly.)
With those things fixed now, bank 1 Seems To Work Fine Now 
(fingers crossed).