I usually build my NPC houses as small as possible (often 10x3 or 8x4). For some reason, especially the 10x3s, I'll get the "not valid housing" message when I try to put a pet in with an NPC. I'm not sure why. With just a workbench and chair, I have 7 tiles of floor space, so that should be plenty. There's enough room for both flags as well. Clearly, there's minimum housing criteria for both a NPC and a pet that exceeds that for just an NPC. Anyone know what that is? The wiki wasn't any help on this one. Thanks!