Here is the full list of all 31 Who's in the Box? achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Beat the game
Put the spell book in the box
Put the spirit board in the box
Put the shampoo in the box
Put the flashlight in the box
Put the teaspoon in the box
Put the corkscrew in the box
Put the doll in the box
Put the card key in the box
Put the artificial eye in the box
Put the gun in the box
Put the swiss army knife in the box
Put the empty cage in the box
Put the guitar in the box
Put the rubber ducky in the box
Put the parrot in the box
Put the milk package in the box
Put the ice axe in the box
Put the canned cat food in the box
Put the megaphone in the box
Put the guinea pig in the box
Put the jackhammer in the box
Put the credit card in the box
Try to put the pillow in the box
Put the toy railway in the box
Try to put the picklock in the box
Try to put the key in the box
Try to put the magic amulet in the box
Try to put the axe in the box
Put the cactus in the box
Try to put the bonsai in the box