Expanding NPC Sprite sheets

This is a useful post, and I'm even more interested in the follow-ups you're planning.

I'm interested in the 15th man / additional PC stuff, and want to get involved in that after I'm done with my current project with battle palettes.

Especially looking forward to the OAM lecture, which I don't know that much about yet.

For my contribution, I know for battle sprites, it pre-computes all the 16x16 sprite tiles for the character. Which are themselves made up of "raw" 8x8 tiles from Rom, which tiles are sometimes flipped or rearranged in different combinations to make up the larger tiles. And then that data sits in a big clump in general working memory, which is where I edit it. The transfer to OAM is thus far a black box to me.

I assume for overworld sprites, they aren't pre-computed all at once like that. Otherwise expanding them like this would cause huge problems.