I love how quirky some of the NPC triggers are in 'Terraria' — the Zoologist is one of those that feels like a little reward for being a critter collector. In my world the Zoologist moved in the moment I had filled out a decent chunk of the Bestiary: I’d captured and logged around twenty different critters (mostly with a Bug Net and some clever trapping), and I had an empty, valid house ready. After those two boxes were ticked — critter progress and a proper home — she popped up at the next check and set up shop, selling various critter- and pet-related items.
She doesn’t care much about where the house is placed biome-wise — I’ve seen her appear in a cozy surface cabin by the forest and also next to my ocean outpost — but she definitely needs the standard NPC housing requirements met (light, background walls, door, table, chair). I also noticed she ignored my world while I was in the middle of a boss fight or underground expedition — she only spawned when I was back on the surface and not in combat. Overall, getting her felt like a cute milestone; I still smile when I see her wares during my town runs.
Setting up a menagerie in 'Terraria' turned one of my bases into a tiny zoo, and the Zoologist NPC felt right at home — which actually matters for your town's happiness. The game's happiness system (and many modded NPCs follow this) checks an NPC's preferred biome, nearby neighbors, and whether their house has the right background walls. The Zoologist usually likes being near critters, natural biomes like the Forest or Jungle, and spaces with lots of pet spawns, so placing them in a leafy, critter-friendly room boosts their individual happiness.
That individual happiness contributes to the overall town mood because each NPC's mood affects shop prices and sometimes special interactions. A happy Zoologist will produce friendlier dialogue and better prices if they sell goods tied to animals or buffs. Conversely, crowding their house near mismatched NPCs or in a biome they dislike will lower their mood, nudging average town happiness down. I ended up building a dedicated animal wing with butterfly statues and bird cages just to keep that Zoologist grinning — it felt oddly rewarding.
I've always loved making little ecosystems in 'Terraria', and the Zoologist feels like the sort of NPC who wants a house that breathes life. I try to give them a cozy wooden house on the surface, close to trees and water, with plenty of natural background walls and potted plants. Big windows or glass walls to let in the sky and critters roaming outside make it feel right. Placing it near a Jungle or Forest biome helps because critters spawn there naturally, and that fits the Zoologist's vibes.
I also avoid putting the house near Corruption, Crimson, or the Underground layers — those places feel wrong for someone who loves critters. Inside I clutter it with bird cages, terrariums, and other nature-themed decorations so it almost feels like a tiny museum of wildlife. When the Zoologist is happy there, I always feel like the town has a heartbeat again.