There are currently a few Secret Rooms on Box Critters. Check out the Guides below to find all the Secret Rooms around Box Critters.
Battle Bears Crash Site:
The Battle Bears Crash Site is currently a Secret Room, you can find it by entering the Jolly Roger’s Cellar room. Once in the room, click over top of the Battle Bears Box in the bottom right side, and you’ll find the Secret Room. There are also a bunch of Hidden Items in this Secret Room, check out my Guide here to find them all!