The Move Furniture cheat under Misc Codes will prevent NPCs from showing up in their houses.
They are still loaded into memory and are visible to the NPC selector, and sometimes even talk to you on their own, but are completely invisible.
To reproduce: enable the Move Furniture cheat, enter an NPC's house with light on (aka a house with a villager inside it).
No cheats enabled.
Move furniture enabled.
The Move Furniture cheat under Misc Codes will prevent NPCs from showing up in their houses. They are still loaded into memory and are visible to the NPC selector, and sometimes even talk to you on their own, but are completely invisible. To reproduce: enable the Move Furniture cheat, enter an NPC's house with light on (aka a house with a villager inside it).
No cheats enabled.
Move furniture enabled.