Does the Companion Cube stab you?
The Companion Cube is a pet summoning item. It has a chance of being sold by the Traveling Merchant for 5. It summons a pet Companion Cube that will jump around the player frantically. When the player and the Companion Cube are in complete darkness, the Cube can occasionally “stab” its owner, inflicting 3 damage.
How large is the Companion Cube?
The scale for this model was made using the in-game physics engine. Stacking 4 cubes high and measuring how long it took a Turret to drop from that height (0.71s), it was determined that the cubes are 24”.

How do you get a Weighted Companion Cube?
Recipe. To create this beautifuly majestic cube that emits hearts when you click on it, place your Weighted Storage Cube on the ground, and then simply right click on it with a poppy. Then you can break your newly created companion and carry it with you.
Do companion cubes have bodies in them?
Perhaps companion cubes are the way that Aperture Science are dealing with the many, many deceased testing subjects. Once the subject dies, they collect the bodies, stuff them into the cubes, and put them away into storage to test later on.
Why is the Companion Cube so expensive?

Companion Cube Purchase Price The reason for this is due to the Companion Cube being a purchase-only item that costs a whopping 5 platinum coins–easily the most expensive item so far added to Terraria.
Is the Companion Cube rare?
The chance of the Travelling Merchant selling the Companion Cube is 1/150 making it a raletively rare item to attain.
Is Companion Cube in Portal 2?
The Companion Cube makes a prominent appearance in the Portal 2: Lab Rat comic, in which it speaks with protagonist Doug Rattmann. This appears to reference Portal, in which GLaDOS states that the Companion Cube cannot speak and, if it does, its advice should be disregarded.