Bunny

Bunnies belong to the surface forest and are usually the first living thing a new character sees. They are harmless, they take damage from anything including you, and they exist mostly as material and decoration. Statues produce them as well, but a statue bunny cannot be netted: swing at one and it puffs out of existence.

Finding bunnies, or the gem colored variants, down in the cavern layer means something civilized is nearby, since they gather around settled areas and around bound NPCs waiting to be freed. In practice that usually points at the Skeleton Merchant or a captive resident somewhere close. It costs nothing to notice and it saves a lot of aimless digging.

Any bug net picks one up for the inventory, and from there it either goes back into the world or into a cage, which is a one way trip unless you shimmer the furniture apart again. Costumed ones are the trap. A party hat, a santa suit or a slime outfit is stripped the moment the bunny goes into a net, so the cage on your wall will always hold a plain one no matter what you caught.

A rare gold version appears in place of a normal bunny now and then and is worth stopping your day for. A Blood Moon flips every loose bunny into its corrupt or crimson counterpart, and that includes any you release while the moon is up, so empty the pet slot before the sky turns red. Vile powder does the same thing on demand. Party hat wearers shrug the powder off, which is a strange little mercy.